HANBBOQKSforSiiidentsundGcneral  Readers 


ZOOLOGY 


MACALISTER 


John  3\vett 


rr 


HANDBOOKS  for  Students  and  General  Readers 
IN  SCIENCE,  LITERATURE,  ART,  AND  HISTORY. 


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The  subjects  and  authors,  so  far  as  selected,  are  as  follows  : 

VOLUMES  PUBLISHED. 

Zoolosry  of  the  Invertebrate  Animals.  By  ALEX.  MACAUSTER, 
M.D.,  Professor  of  Zoology  and  Comparative  Anatomy  in  the  University 
of  Dublin.  Special! v  revised  tor  America  by  A.  S.  PACKARD,  JR., 
M  p.,  Professor  of  Zoology  and  Geology  in  Brown  University.  60  cts. 
This  and  the  following  together  in  one  vol.,  $1.00. 

Zoology  of  the  Vertebrate  Animals.  By  the  above  authors. 
i6;no.  60  cents.  This  and  the  preceding  together  in  one  vol.,  $1.00. 

Zoology.     The  preceding  two  volumes  in  one.  i6mo,  $1.00. 

The  Studio  Arts,     By  ELIZABETH  WINTHROP  JOHNSON.     i6mo.     6oc. 

Astronomy.  By  R.  S.  BALI.,  LL.D.,  F.R.S..  Astronomer  Royal  for 
Ireland.  Specially  Revised  for  America  by  SIMOV  NKWCOMB.  Superin- 
tendent American  Nautical  Almanac ;  formerly  Professor  at  the  U.  S. 
Naval  Observatory.  i6mo.  6oc. 

Practical  Physics— Molecular  Physics  and  Sound.  By 
FREDERICK  GUTHRIE,  PH.D.  F.R.SS.  L.  &  E.,  Professor  of  Physics  in 
the  Royal  Scho  ,1  of  Mines,  London.  i6mo.  6oc.  (See  Practical 
Physics  below.) 

FORTHCOMING    VOL UMES. 

Architecture.  By  RUSSELL  STURGIS,  A.M.,  Architect,  Professor  of 
Arcmtecture  and  the  Arts  of  Design,  in  the  College  of  the  City  of  N.  Y. 

Botany.  Morphology  and  Physiology.  By  W.  R  McNAB, 
M  D..  F.L.S.,  Professor  of  Botany,  Royal  College  of  Science  for 
Ireland,  Dublin.  Revised  by  C.  E.  BESSEY,  M.S.,  Professor  of 
Botany  in  the  Iowa  Agricultural  College. 

Botany.     Classification  of  Plants.    By  W.  R.  McNAB.    Revised 

by  C.  E.  BESSEY. 
English  Language.    By  T.  R.  LOUNSBURY,  Professor  in  Yale  College. 

English  Literature.    By  

French  Literature.     By  FERDINAND  BOCHER,  Professor  in  Harvard 

University. 

German  Literature.    By 

History  of  American  Politics.     By  ALEXANDER  JOHNSTON,  A.M. 
Jurisprudence.      By   JOHNSON  T.    PLATT,   Professor    in    the    Law 

Department  of  Yale  College. 

Practical     Physics— Electricity     and     Magnetism.       By 

Prof.  F.  GUTHRIE,  Ph.D. 
Practical  Physics— Heat  and  Light.     By  Prof.   F.   GUTHRIE, 

Physical  Geography.  By  CLARENCE  KING,  Director  of  the  U.  S. 
Government  Surveys. 

Political  Economy.  *  By  FRANCIS  A.  WALKER,  Ph.D.,  Professor  in 
Yale  College. 


HANDBOOKS  for  Students  and  General  Readers 


ZOOLOGY 


BY 


ALEX.   MACALISTER,  M.D. 

Professor  of  Zoology  and  Comparative  Anatomy  in  the 
University  of  Dublin 


Specially  Revised  for  America 


A.  S.  PACKARD,  JR.,  M.D. 

Professor  of  Zoology  and  Geology  in 
Brotvit  University 


TWO    VOLUMES    IN    ONE 


NEW   YORK 

HENRY  HOLT  AND  COMPANY 
1879 


HANDBOOKS  for  Students  and  General  Readers. 


ZOOLOGY 


OF   THE 


INVERTEBRATE    ANIMALS 


BY 

ALEX.    MACALISTER,    M.D. 

Professor  of  Zoology  and  Comparative  Anatomy  in  tke 
University   of  Dublin. 


Specially  Revised  for  America 


A.  S.  PACKARD,  JR.,  M.D. 

Professor  of  Zoology  and  Geology  in 
Brown  University. 


NEW  YORK 

HENRY  HOLT   AND  COMPANY 
1879. 


COPYRIGHT,  1879, 

BY 

HENRY    HOLT    &    CO. 


PRINTED  BY  TROVES  PRINTING  AND  BOOKBINDING  CO.,  NEW  YORK. 


EXPLANATORY. 


THIS  Series  is  intended  to  meet  the  requirement  of 
brief  text-books  both  for  schools  and  for  adult  readers 
who  wish  to  review  or  expand  their  knowledge. 

The  grade  of  the  books  is  intermediate  between  the 
so-called  "primers"  and  the  larger  works  professing 
to  present  quite  detailed  views  of  the  respective  sub- 
jects. 

Such  a  notion  as  a  person  beyond  childhood  re- 
quires of  some  subjects,  it  is  difficult  and  perhaps 
impossible  to  convey  in  one  such  volume.  Therefore, 
occasionally  a  volume  is  given  to  each  of  the  main 
departments  into  which  a  subject  naturally  falls — for 
instance,  a  volume  to  the  Zoology  of  the  vertebrates, 
and  one  to  that  of  the  invertebrates.  While  this  ar- 
rangement supplies  a  compendious  treatment  for  those 
who  wish,  it  will  also  sometimes  enable  the  reader 
interested  in  only  a  portion  of  the  field  covered  by  a 
science,  to  study  the  part  he  is  interested  in,  without 
getting  a  book  covering  the  whole. 

Care  is  taken  to  bring  out  whatever  educational 
value  may  be  extracted  from  each  subject  without  ira- 


vi  Explanatory, 

peding  the  exposition  of  it.  In  the  books  on  the 
sciences,  not  only  are  acquired  results  stated,  but  as 
full  explanation  as  possible  is  given  of  the  methods  of 
inquiry  and  reasoning  by  which  these  results  have 
been  obtained.  Consequently,  although  the  treatment 
of  each  subject  is  strictly  elementary,  the  fundamental 
facts  are  stated  and  discussed  with  the  fulness  needed 
to  place  their  scientific  significance  in  a  clear  light, 
and  to  show  the  relation  in  which  they  stand  to  the 
general  conclusions  of  science. 

Care  is  also  taken  that  each  book  admitted  to  the 
series  shall  either  be  the  work  of  a  recognized  author- 
ity, or  bear  the  unqualified  approval  of  such.  As  far 
as  practicable,  authors  are  selected  who  combine 
knowledge  of  their  subjects  with  experience  in  teach- 
ing them. 


PREFACE. 


THE  STUDENT  who  would  acquire  a  satisfactory 
knowledge  of  the  principles  of  Zoology  is  recom- 
mended to  commence  by  learning  the  elementary 
principles  of  General  Biology ;  and  having  mastered 
these  he  should  then  study  the  groups  of  the  Inverte- 
brates as  here  detailed,  coupling  his  study  with  a 
practical  examination  of  such  common  types  as  are 
easily  to  be  obtained.  A  jellyfish,  or  a  hydra,  an 
earthworm,  an  oyster,  a  snail,  a  cockroach  and  a 
lobster,  are  forms  everywhere  procurable,  and,  if 
examined,  will  give  the  student  a  good  general  idea 
of  the  structure  of  Invertebrate  Animals.  It  must  be 
borne  in  mind  that  without  some  such  practical  study, 
no  amount  of  reading  will  suffice  to  convey  accurate 
and  adequate  ideas  of  animal  organisation. 

ALEXANDER  MACALISTER. 


CONTENTS. 


CHAPTER  I. 

PAGE 

Nature  of  Animals — Processes  of  Life — Tissues  and  Organs 
— Symmetries  of  Animals I 

CHAPTER  II. 

Classification  of  Animals — Method  of  naming — Resem- 
blances of  Relationship  and  of  Adaptation— Mimicry — • 
Parasites — The  Seven  Sub-kingdoms  of  Invertebrate 
Animals— Each  Animal  has  a  Life  History,  not  a  mere 
Growth— Rudimental  Organs— Tendency  to  Individual 
Variety 6 


CHAPTER  III. 

Conditions  of  Distribution  in  Time  and  Space— Freshwater, 
Marine,  and  Terrestrial  Life— Methods  of  Study  of 
Zoology 13 


CHAPTER  IV. 

Sub-kingdom    i.     Protozoa  :  Rhizopods— Amoebae— Sun- 
Animalcules — Gregarines  and  Radiolarians  .        .         .18 


Contents. 


CHAPTER  V. 

PAGB 

Infusion-Animals — Luminous    Animalcules — Summary    of 
the  Forms  in  Sub-kingdom  I 25 

CHAPTER  VI. 
Sub-kingdom  2.     Sponges       ......     28 

CHAPTER  VII. 

Sub-kingdom  3.  Ccelenterate  Animals :  Hydras — Sea-Firs, 
Medusae 52 

CHAPTER  VIII. 

Sea- Anemones — Corals — '  Dead  Men's  Toes ' — Sea-Pens  .    41 

CHAPTER  IX. 

Sub-kingdom  4.     Echinodermata :  Stone-Lilies — Feather- 
Stars—Starfishes         47 

CHAPTER  X. 

Sea  Urchins — Sea  Cucumbers — Summary  of  Forms  in- 
cluded in  Sub-kingdom  4 52 

CHAPTER  XL 

Sub-kingdom  5.     Worms  :  Turbellarians— Tape- Worms- 
Flukes— Round  and  Thread- Worms    ....     57 

CHAPTER  XII. 

Wheel-Animalcules — Spoon-Worms—Leeches.        .        .     66 


Contents.  xi 


CHAPTER  XIII. 

PACK 

Bristled- Worms  —  Earth-Worms  —  Summary   of  Normal 
Worms 70 


CHAPTER  XIV. 
Aberrant- Worms — Moss-Polyps  and  Tunicated  Animals    .     74 

CHAPTER  XV. 

Sub-kingdom  6.     Mollusca  or  Soft-bodied  Animals  :  Class 
I.  Arm-footed  Molluscs;  Class  2.     Bivalves        .        .     78 

CHAPTER  XVI. 

Class  3.    Head-bearing  Molluscs :  Whelks,  Snails,  &c.     .    84 

CHAPTER  XVII. 

Class  4.    Cuttle-Fishes—Nautili  and  Squids— Summary  ot 
Characters  of  the  Classes  of  Mollusca  ....     90 

CHAPTER  XVIII. 
Sub-kingdom  7.     Jointed  Animals  or  Arthropoda     .         .     96 

CHAPTER  XIX. 
Class  I.     Crustacea  :  Crabs,  Loboteis,  Shrimps,  &c.        .     98 

CHAPTER   XX. 

Class  2.     Spiders,  Mites,  and  Scorpions .         .         .  108 


xii  Contents. 


CHAPTER  XXI. 

PACK 

Class  3.    Myriopoda,  Centipedes,  and  Gaily- Worms        .  112 


CHAPTER  XXII. 

Class  4..  Insecta :  Insects — General  Characters  and  Struc- 
ture   115 

i 

CHAPTER  XXIII. 
./ 

Orders  of  Insects  whose  Metamorphoses  are  Imperfect — • 
Aphides,  Bugs,  Straight-winged  Insects  and  Dragon- 
Flies  123 

i   /  \ , 

.  CHAPTER  XXIV. 
Insects  whose  Metamorphoses  are  complete      •        »         .  127 

INDEX  and  GLOSS4RY    ,  .  137 


INVERTEBRATA. 


CHAPTER  I. 

GENERAL   CHARACTERS   OF  ANIMALS. 

Physical  Conditions  of  life. — An  animal,  chemically 
considered,  consists  of  a  few  elements  l  united  into 
extremely  unstable  combinations,  which  are  at  every 
moment  undergoing  chemical  change.  The  consti- 
tuent materials  are  constantly  becoming  grouped  into 
more  simple  and  stable  compounds,  and  in  that  state 
they  are  either  eliminated  or  retained  in  an  inactive 
condition,  while  other  materials  from  without  are 
being  taken  in,  and  so  modified  that  they  replace  the 
molecules  removed  by  the  previous  decomposition. 
As  long  as  life  lasts,  these  conditions  of  waste  and  re- 
pair continue  ;  so  that  the  particles  of  the  bodies  of 
al  lanimals  are  in  a  state  of  constant  change. 

The  food  of  animals  contains  carbon,  hydrogen, 
nitrogen,  and  oxygen,  which  must  be  grouped  into 
complex  molecules  before  the  animal  can  use  them 
for  his  nutrition.  Combinations  of  the  requisite  com- 
plexity can  be  derived  only  from  previously  organised 

1  Carbon,  hydrogen,  oxygen,  and  nitrogen. 
B 


2  Invertebrate*. 

^materials  either  iiiimal  or  vegetable.  In  most  vege- 
tables the  forces  concerned  in  assimilation  are  suffi- 
^  q^it ,  to^  bre^  uj>  originally  stable  compounds,  such 
'as  carbonic"  acid,  ahcTto  induce  the  elements  to 
combine  into  the  unstable  combinations  of  which 
living  textures  consist 

The  process  of  repair  in  animals  has  three  stages, 
ist,  the  taking  in  of  material  as  food;  2nd,  the  chang- 
ing of  food  into  a  substance  capable  of  forming  part 
of  the  living  organism,  i.e.  blood ;  and  3rd,  the  laying 
down  of  this  assimilated  material  in  the  tissues  of  the 
body  of  which  it  thus  becomes  a  constituent,  replacing 
the  losses  sustained  by  each  organ  in  each  discharge 
of  its  function. 

For  the  life-processes  of  animals  oxygen  is  necessary, 
and  special  structures,  called  respiratory  or  breathing 
organs,  are  often  provided  for  taking  it  in.  The  car- 
bonic acid  formed  from  the  waste  of  the  tissues  is 
usually  got  rid  of  by  these  organs. 

The  material  with  which  the  vital  properties  are 
connected  is  of  the  same  nature  in  all  animals  and  is 
called  protoplasm.  The  simplest  animals  are  mere 
masses  of  this  substance,  which  in  them  discharges  all 
the  fjnctions  needful  for  the  maintenance  of  life  ;  the 
more  complex  are  built  up  of  aggregations  of  particles 
of  the  same  material,  or  of  substances  derived  from  it 
in  the  course  of  growth.  Each  of  these  constituent 
particles  or  cells,  as  they  may  conveniently  be  called, 
usually  consists  of  a  mass  of  protoplasm  surrounded 
by  an  envelope  of  some  material  derived  by  chemical 
action  from  protoplasm. ,  Ceils  continuously  grouped 
make  up  tissues,  and  a  group  of  tissues  which 


General  Characters  of  Animals.  3 

performs  any  special  duties  in  the  life  of  an  animal 
is  called  an  organ.//  While  there  are  thus  varying 
degrees  of  complexity  among  animals,  yet  the  parts 
of  a  simple  animal  have  to  perform  as  many  essential 
functions  as  those  of  a  more  complex  animal,  the  in- 
crease in  complexity  of  an  organism  being  correlated 
not  with  an  increase  in  the  number  of  essential  functions 
but  with  the  need  for  the  more  perfect  fulfilment  of 
existing  duties.  Increase  in  complexity  thus  results 
from  division  of  labour,  and,  with  each  increase,  the 
sphere  of  the  functional  activity  of  each  part  becomes 
narrowed.  For  example,  in  jelly-fishes  one  set  of 
cavities  act  as  organs  of  digestion  and  of  circulation, 
while  in  higher  animals  these  functions  have  separate 
organs,  and  even  subsidiary  portions  of  these  great 
functions  have  for  their  accomplishment  distinct  parts. 

Functions. — Three  sets  of  functions  are  discharged 
by  organs  in  the  body  of  an  animal  :  namely,  ist, 
those  of  Relation  ;  2nd,  those  of  Nutrition  ;  3rd,  those 
of  Reproduction. 

The  organs  appropriated  to  the  functions  of  Rela- 
tion are  those  which  connect  the  animal  with  its 
environ  ng  conditions,  informing  it  about  its  surround- 
ings, and  enabling  it  to  avoid  disagreeable  or  to  court 
agreeable  external  influences.  These  organs  are  of  two 
kinds  :  (A)  those  of  sensation,  such  as  the  skin,  or  organ 
of  touch,  and  the  special  sense  organs  (eye,  ear,  nose, 
tongue),  and  (B)  those  of  motion,  which  may  be  of 
three  kinds,  (a)  inconstant  processes  of  protoplasm 
called  pscudopodia  (fig.  8),  (b)  minute,  constant,  hair- 
like  processes  having  the  power  of  waving  to  and 
fro,  called  cilia,  or  (c]  contractile  cells  and  fibres  in 
B  2 


4.  Invertebrates 

bundles  called  muscles.  The  first  kind  occur  in  the 
lowest  animals  and  in  naked  protoplasmic  particles ; 
the  second  in  infusorial  animals  (fig.  14) ;  the  third  in 
all  but  the  simplest  animals.  Connected  with  the 
organs  of  relation  we  find  a  system  of  fine  white  threads 
called  nerves,  whose  endings  occur  in  these  organs, 
and  whose  starting-points  are  central  clusters  of  nerve- 
cells,  called  ganglia.  These  threads  convey  the 
variously  received  stimuli  from  the  sense  organs  to 
the  ganglia,  and  carry  the  command  for  motion  from 
the  ganglia  to  the  muscles. 

The  function  of  Nutrition  is  discharged  by  four 
sets  of  organs  :  ist,  those  of  feeding,  consisting  of  a 
cavity  or  stomach,  for  the  reception  of  the  food,  with 
glands  appended  thereto,  which  secrete  fluids  to  assist 
in  assimilation  ;  2nd,  organs  of  circulation,  which  carry 

FIG. 


Euplotes  Charon,  a  ciliated  infusorium  showing  the  stages  of  division. 

the  assimilated  matter,  or  blood,  through  the  body  for 
the  nutrition  of  the  tissues ;  3rd,  organs  of  respiration, 
by  which  oxygen  is  taken  in ;  and  4th,  organs  of 
excretion  whereby  the  waste  products  are  eliminated. 


General  Characters  of  Animals.  5 

There  are  three  stages  in  the  contest  between  waste 
and  repair  which  is  characteristic  of  life.  In  the  first, 
repair  is  in  excess  of  waste,  and  individual  growth 
proceeds  until  a  definite  limit,  constant  within  certain 
bounds  for  each  specres,  is  reached.  When  this  is 
attained,  excess  of  nutrition  still  continues  but  tends 
to  become  separate  and  independent  ;  by  such  dis- 
continuous modes  of  growth,  the  third  set  of  functions, 
or  Reproduction,  is  accomplished.  Of  this  there  are 
three  chief  forms  :  (A)  either  the  whole  body  of  the 
parent  may  split  into  two  or  more,  each  becoming  a 
perfect  animal  like  its  parent  ;  this  process  is  named 
fission.  (B)  In  the  second  mode  of  reproduction  a  small 
portion  of  the  body  of  the  parent  animal  enlarges  and 
becomes  detached  as  a  bud,  which  develops  directly 
into  an  organism  like  its  ancestor  ;  this  is  called  gem- 
mation, (c)  In  the  third  mode  small  particles  FIG.  2. 
called  eggs  arise  from  the  tissues  of  the 
parent,  and  on  being  fertilised,  are  capa- 
ble of  developing  into  new  individuals ; 
this  is  called  ovulation. 

The  second  stage  of  existence  having 
for  a  time  continued,  the  organism  reaches 
a  third  stage,  in  which  waste  exceeds 
repair,  and  as,  by  degrees,  the  assimilated 
material  becomes  insufficient  to  keep  up  Gemmation  ;n 
the  processes  of  life  this  stage  terminates  Hydra  viridit. 
in  death. 

Summary. — Animals  consist  for  the  most  part  of 
protoplasm,  are  constantly  undergoing  waste,  and 
being  built  up  by  the  assimilation  of  food.  They 
differ  from  plants  in  being  usually  capable  of  loco- 


6  Invertebrate 

motion  (though  this  has  exceptions),  in  being  only 
capable  of  assimilating  organic  matter  (except  in  the 
case  of  water  and  oxygen),  and  in  having  their  cell- 
walls  composed  of  nitrogenous  matter,  while  in  plants 
non-nitrogenous  matter  abounds.  Higher  animals  are 
strongly  differentiated  from  plants  ;  the  lower  forms  are 
often  of  doubtful  position.  Animals  may  be  simple  or 
complex,  complexity  depending  on  division  of  labour, 
and  the  consequent  specialisation  of  function  in  organs 
which  become  differentiated  from  each  other.  The 
chief  functions  are  Relation,  Nutrition  and  Reproduc- 
tion, the  latter  taking  place  during  the  stage  when 
individual  growth  has  ceased  and  while  as  yet  repair 
exceeds  waste. 


CHAPTER  II. 

ORGANS  AND   CLASSIFICATION   OF  ANIMALS. 

Method  of  Study.— The  first  branch  of  zoology 
necessary  to  be  studied  is  the  anatomy  of  the  organism, 
and  the  best  method  of  study  is  the  examination  of 
some  of  the  commoner  types  of  each  class.  As  many 
of  these  are  small,  and  optical  assistance  necessary, 
the  student  should  provide  himself  with  a  good  pocket 
lens.  For  dissection,  the  instruments  required  are,  a 
scalpel,  a  fine-pointed  pair  of  dissecting  forceps,  and 
several  sharp-pointed  needles  fixed  in  wooden  handles 
and  with  their  extremities  ground  flat,  so  as  to  cut  as 
well  as  tear.  As  many  small  animals  can  be  most  easily 
dissected  under  water  it  is  convenient  to  have  a  shallow 


Organs  and  Classification  of  Animals.       f 

wooden  tray  lined  with  sheet  lead  for  the  purpose,  while 
it  often  facilitates  dissection  to  have  a  thin  sheet  of  cork 
weighted  with  lead,  so  as  to  retain  its  position  at  the 
bottom  of  the  fluid  upon  which  the  various  parts  may 
be  pinned  down.  To  preserve  animal  organs  the 
best  materials  are,  spirits  of  wine,  or  a  weak  (2  per 
cent.)  solution  of  bichromate  of  potassium. 

The  study  of  the  forms,   nature  and  relations  of 
organs  to  each  other  and  to  the  organism  in  general, 

FIG. 


Common  orange  Star-fish  (Astropecten  aurantiacus). 


and  the  laws  deduced  therefrom  is  known  as  Morpho- 
logy ;  the  study  of  the  uses  of  parts  is  called  Physiology. 


8  Invertebrata. 

Morphology. — Groups  of  organs  are  generally  sym- 
metrically disposed  in  animals ;  either  they  are  arranged 
in  order  around  a  central  point  in  one  plane,  or  else  each 
individual  consists  of  a  succession  of  similar  segments, 
as  in  a  centipede.  In  the  first  case  the  symmetry  is 
said  to  be  radial  as  in  the  star-fish  (fig.  3)  ;  in  the 
second  the  segments  are  each  made  up  of  two  sym- 
metrical halves,  and  the  symmetry  is  said  to  be 
bilateral 

In  a  perfectly  symmetrical  animal  all  the  organs 
should  be  proportionally  developed,  but  as  the  vary- 
ing conditions  of  animal  existence  often  require  the 
more  extensive  performance  of  some  duties  than  of 
others,  we  always  find  that  some  organs  are  larger, 
others  smaller.  In  fact  animals  are  so  perfectly  fitted 
to  their  surroundings  that  could  we  know  all  the  con- 
ditions under  which  a  given  animal  existed,  we  could 
form  a  good  conception  of  its  structure  and  vice  versd. 

The  Embryo. — To  understand  the  true  relations  of 
structures  in  animals  it  is  necessary  to  watch  the  growth 
of  the  organism  from  the  earliest  stages  of  its  produc- 
tion in  the  egg  until  it  attains  its  adult  condition.  The 
embryo  is  not  a  simple  miniature  of  the  full  grown 
animal,  but  reaches  its  perfect  state  by  undergoing  a 
series  of  changes,  which  follow  each  other  in  a  definite 
order.  In  this  process,  parts  and  organs  start  into  being 
which  were  before  unnoticeable,  and  some  of  these  have 
only  a  transient  existence  fading  off  into  nothingness. 
Thus  the  common  acorn  shell  emerges  from  its  egg  as  a 
little  free-swimming  larva  (fig.  4),  with  eyes  and  feelers, 
but  these  totally  vanish  in  the  adult  (fig.  5) ;  such  organs 
are  known  as  provisional  organs,  and  occasionally  they 


Organs  and  Classification  of  A  nimals.       9 

leave  traces  behind  when  their  functions  have  ceased, 
like  the  cord-like  obliterated  embryonic  blood-vessels 
in  mammalia.  In  some  animals,  during  their  develop- 
ment, organs  spring  into  being  for  a  shorter  or  longer 
period,  but  never  perform  any  function  and  either  vanish 

FIG.  4. 


Larva  of  common  Acorn-shell  (Balanus porcatus),  showing  antennae  («), 
limbs  (b\  and  eye  (d). 

or  remain  permanently  in  an  undeveloped  condition ; 
such  organs  are  called  rudimental,  and  they  are  always 
such  as  in  some  kindred  form  discharge  an  important 
duty.  Thus  most  cuttle-fishes  have  a  groove  in  their 
body  during  their  embryonic  life,  which  closes  in  and 
forms  a  cavity  wherein  the  internal  shell  is  secreted;  but 


10 


Invertebrate* 


FIG.  5. 


the  octopus  or  sea-spider,  a  closely  allied  form,  has  a 
similar  groove  which  vanishes,  leaving  no  trace  behind. 
Instances  of  the  kind  might  be  multiplied,  as  there  is 
scarcely  an  individual  form  in  the  higher  sub-kingdoms 
which  does  not  in  its  life  history  exhibit  instances  of 
provisional  and  rudimental  organs. 

Characters  Essential  and  Adaptive.— In  each 
animal  we  can  divide  the  characters  into  two  groups, 

essential  and  adaptive; 
the  former  of  these  are 
those  whereby  we  can 
learn  the  relations  of 
animals  among  them- 
selves, and  these  are  of 
primary  importance  in 
classification  ;  the  latter 
show  the  relations  of 
the  animal  to  its  sur- 
roundings, but  these  in 
the  adult  often  so  overlie 
the  essential  characters 
as  to  obscure  them.  A  study  of  the  embryogeny  of 
the  animal  will  enable  us  to  understand  its  relation- 
ship, for  the  adaptive  characters  are  of  later  origin 
than  the  essential  and  may  be  traced  as  they  are 
becoming  superinduced.  Thus  among  the  parasitic 
mites  of  the  genus  Pentastoma,  we  could  not  know 
the  true  relations  of  the  worm-like  adults  if  we  were 
not  acquainted  with  the  limb-bearing  larva. 

Classification  and  Nomenclature.— The  animal 
kingdom  is  a  vast  assemblage  of  individuals,  and 
we  require  to  arrange  these  in  larger  categories  for 


Adult  form  of  Balanus  porcatus. 


Organs  and  Classification  of  Animals.      II 

purposes  of  study.  Those  individuals  which  are 
so  far  identical  in-  structure  as  to  lead  us  to  believe 
that  they  are  descended  from  common  parents  we 
speak  of  as  belonging  to  the  one  species.  Species 
is  thus  our  unit  in  systematic  zoology,  but  as  two  in- 
dividuals are  seldom  absolutely  identical  in  all  respects 
specific  distinctions  must  be  more  or  less  arbitrary.  A 
group  of  allied  species  embodying  the  same  structural 
ideas  is  called  a  genus.  An  assemblage  of  allied 
genera  is  a  family  ;  a  group  of  related  families  make 
up  an  order ;  while  related  orders  make  up  a  class,  and 
the  several  classes  included  in  the  animal  kingdom 
are  united  in  certain  primary  categories  called  sub- 
kingdoms.  Systematic  zoologists  give  a  Latin  name  to 
each  of  these,  and  for  convenience  each  species  is 
designated  by  a  Latin  word  to  which  is  prefixed  the 
name  of  the  genus.  The  specific  name  is  generally 
an  adjective,  the  generic  is  a  substantive,  and  should 
be  written  with  a  capital  letter.  Thus  the  dog  is  called 
by  zoologists  Canis familiaris,  Canis  being  the  generic, 
familiaris  the  specific  name.  Canis  aurats  is  the 
jackal,  Canis  lupus  the  wolf.  That  species  in  a  genus 
which  most  strikingly  embodies  the  generic  characters 
is  the  type  of  the  genus.  We  also  speak  of  the  type  of 
a  family,  of  an  order,  or  of  a  class,  the  type  being  that 
species  which  displays  most  clearly  the  characters  of 
the  group  ;  and  for  convenience  we  attribute  certain 
characters  to  ideal  types  to  illustrate  truths  in  classifi- 
cation. 

The  type  genus  usually  gives  its  name  to  the  family  , 
thus  the  dog-family  is  called  Canidae. 

Homology. — In  comparing  animals,  the  most  im- 


12  Invertebrata. 

portant  resemblances  are  those  which  depend  on 
common  relationship  to  the  types  of  the  class  to  which 
they  belong.  These  likenesses  are  called  resemblances 
of  morphological  type.  Thus  if  we  compare  a  dog  and 
a  crow,  we  find  in  both  a  skeleton,  a  brain,  a  skull, 
four  limbs,  a  heart  &c.,  and  we  refer  them  both  to  the 
vertebrate  type,  inasmuch  as  they  both  embody  the  ideas 
of  structure  characteristic  of  vertebrate  animals.  Each 
part  in  one  is  said  to  be  homologous  with  the  corre- 
sponding part  in  the  other,  the  wing  with  the  fore  leg, 
&c.  Homology  is  thus  identity  of  structure  irrespec- 
tive of  function,  and  parts  are  homologous  which 
represent  the  same  parts  in  the  ideal  type  of  the  class. 
Such  resemblances  are  the  bases  of  classification. 

Analogy. — Likenesses  of  parts  may  also  depend  on 
similarity  of  function  ;  thus  the  wings  of  insects  and  the 
FIG.  6.    ^  wings  of  birds   are  used   for 

the  same  purpose,  and  have 
certain  resemblances.  These 
similarities  are  called  resem- 
blances of  analogy,  and  they 
tell  us  nothing  as  to  the  nature 
of  the  organs  compared. 

Mimicry. — Animals  of  de- 
finite geographical  areas  often 
resemble  each  other  in  some 
.    respects  :    thus  they  may  be 

Leaf  insect    (Phylhwn  siccifo-  '   .      .  .  J  J 

Hum).  mostly     similar     in      colour, 

mostly  white,  or  spotted,  or  striped,  or  brightly 
coloured.  Sometimes  animals  mimic  in  shape  or  colour 
the  leaves  and  twigs  on  which  they  live  (fig.  6),  or 
the  prevalent  colour  of  the  heibage.  Thus  the  Kakapo 


Classification  and  Distribution  of  Animals.  13 

or  ground  parrot  of  New  Zealand,  which  can  hardly  fly, 
is  in  plumage  like  the  mottled  green  vegetation  among 
which  it  lives.  The  ptarmigan  and  other  birds  become 
white  in  winter,  so  as  to  become  inconspicuous  among 
the  snow.  Sometimes  an  insect  mimics  in  appearance 
another  of  different  nature  living  in  the  same  district. 
In  such  cases  the  insect  imitated  is  one  which,  from  its 
disagreeable  secretions  or  sting,  is  not  a  favourite  prey 
of  insect-eaters.  Hence  the  mimicry  protects  the 
imitator,  who  is  usually  rarer  than  the  insect  imitated. 

Organs  which  are  homologous  consist  of  homo- 
logous parts  ;  and  as  this  is  not  the  case  in  organs  re- 
sembling each  other  only  in  function,  we  must  be 
careful  to  discriminate  morphological  from  physio- 
logical likeness. 

In  animals  which  consist  of  successive  segments  in 
a  chain,  like  centipedes  or  lobsters,  each  segment  is 
composed  of  parts  similar  to  those  of  its  neighbouring 
joints.  Such  parts  are  said  to  be  serial  homologues, 
as  for  example  the  fore  and  hinder  limbs  of  quad- 
rupeds. 

CHAPTER  III. 

CLASSIFICATION   AND   DISTRIBUTION   OF  ANIMALS. 

Sab-Kingdoms. — THE  animal  kingdom  includes  eight 
sub-kingdoms.  In  these  we  observe  a  certain  pro- 
gressive increase  in  complexity,  from  one  end  of  the 
series  to  the  other  ;  but  they  do  not  make  a  linear 
series,  as  the  highest  organism  of  each  is  in  no  degree 
related  to  the  lowest  organism  of  the  next  sub-kingdom, 
being  usually  much  more  advanced  and  specialised,  so 


,  14  Inverlebrata. 

that  in  point  of  complexity  the  sub-kingdoms  overlap 
each  other. 

The  first  sub-kingdom,  Protozoa,  includes  those 
animals  which  have  neither  body-cavity  nor  nervous 
system,  and  are  single  celled. 

Sub-kingdom  2.  Polystomata,  includes  sponges, 
which  have  an  internal  cavity  with  a  three  layered  wall, 
one  outlet,  and  usually  many  inlets,  but  no  differ- 
entiated organs,  though  consisting  of  many  cells. 

Sub-kingdom  3.  Coslenterata,  includes  jelly-fishes 
and  sea  anemones,  having  a  stomach  cavity  and  a 
body  cavity  as  an  outgrowth  therefrom,  and  a  radiate 
symmetry. 

Sub-kingdom  4.  Echinodermata,  includes  star- 
fishes and  sea-urchins,  with  a  body  cavity  separate 
from  the  stomach,  a  nervous  system,  and  a  system  of 
water-tubes  which  are  agents  in  locomotion. 

Sub-kingdom  5.  Vermes,  includes  worms  which 
are  bilaterally  symmetrical,  and  composed  of  successive 
similar  segments,  with  no  jointed  limbs,  and  with  a 
water- vascular  system  which  has  no  locomotory  func- 
tion. 

Sub-kingdom  6.  Mollusca,  includes  oysters,  snails, 
&c.,  possessing  soft  bodies  enveloped  in  a  leathery 
mantle,  no  jointed  limbs,  a  circulating  system,  often 
an  external  shell  and  often  an  unsymmetrical  nervous 
system. 

Sub-kingdom  7.  Arthropoda,  includes  crabs, 
lobsters,  spiders,  and  insects,  which  have  bodies  made 
up  of  successive  joints,  with  a  symmetrical  nervous 
system,  an  external  skeleton  and  jointed  limbs. 

Sub-kingdom    8.      Vertebrata,    including    fishes, 


Classification  and  Distribution  of  Animals.  15 

reptiles,  birds  and  quadrupeds,  which  have  an  internal 
skeleton,  a  brain  and  vertebral  column.  This  one 
sub-kingdom  includes  the  most  complex  of  animals 
whose  structure  requires  more  minute  examination 
than  does  that  of  the  other  sub-kingdoms.  We  will 
in  the  present  volume  consider  the  seven  invertebrate 
sub-kingdoms. 

In  comparing  these  sub-kingdoms,  we  speak  of 
forms  as  being  high  or  low  in  organisation  according 
to  the  degree  in  which  special  parts  are  appropriated 
for  the  discharge  of  special  functions.  We  also  notice 
that  no  organ  appears  for  the  first  time  in  animals  in 
a.  state  of  complexity,  but  on  the  contrary,  there  is 
always  in  lower  forms  a  prophetic  foreshadowing  of  it 
in  the  modification  of  some  part  already  existing. 

Distribution.— Every  species  of  animal  is  limited  to 
a  definite  geographical  area.  Thus  the  earth's  surface 
may  be  divided  into  regions,  each  characterised  by 
special  inhabitants,  and  the  collected  animals  of  any 
region  we  speak  of  as  its  fauna.  As  a  rule,  life  increases 
in  amount  in  any  country  with  increasing,  and  dimi- 
nishes with  diminishing  temperature.  Thus  the  fauna 
of  a  tropical  exceeds  that  of  a  temperate  region.  The 
number  of  animals  is  also  larger  when  the  difference 
between  the  winter  and  summer  temperature  is  small, 
than  in  a  country  with  the  same  mean  temperature  but 
with  a  greater  range  between  maximum  and  minimum. 
Moisture  is  also  favourable  to  animal  life,  and  the 
fauna  of  a  moist  exceeds  that  of  a  dry  region,  other 
things  being  equdl. 

Many  animals  live  in  places  from  which  light  is 
excluded,  as  in  caves  ;  these  have  rudimental  eyes,  and 


1 6  Invertebrate. 

are  white  or  colourless.  Many  large  caves,  like 
those  of  Kentucky,  Adelsberg  £c.,  have  thus  peculiar 
blind  faunae. 

Sometimes  the  presence  of  one  animal  prevents 
the  diffusion  of  others ;  thus  in  Africa  the  tzetze  fly 
renders  whole  tracts  uninhabitable  by  oxen  and  deer, 
which  are  destroyed  by  its  poisonous  bites. 

The  fauna  of  a  limited  area  of  a  continent  usually 
exceeds  that  of  an  island  of  equal  size  in  its  number 
of  specific  forms  ;  and  the  fauna  of  an  island  lying  near 
a  continent  resembles  that  of  its  neighbouring  con- 
tinent. Oceanic  islands  or  those  isolated  by  very 
deep  straits  have  often  remarkable  faunae  of  their  own, 
e.g.,  the  Galapagos  and  New  Zealand. 

Tropical  species  are,  as  a  rule,  more  limited  in 
range  tnan  are  those  of  temperate  climates,  and  simpler 
animals  are  usually  more  widely  distributed  than  are 
the  more  complex. 

Fresh-water  inhabitants  are  the  fewest  specifically, 
and  as  a  rule  are  simpler  in  organisation  than  allied 
forms  inhabiting  other  media.  The  fourth  sub-kingdom 
has  no  fresh-water  representatives  ;  the  second  has  only 
two,  and  the  third  only  five  species  living  in  this 
medium ;  while  the  others  are  not  very  numerously 
represented  in  fresh-water. 

The  sea  is  the  home  of  nine-tenths  of  the  inver- 
tebrates (if  we  exclude  insects),  and  there  are  also 
definite  ranges  of  extension  to  be  noticed  in  the 
cases  of  marine  species.  The  conditions  limiting 
specific  life  in  the  sea  are  depth,  cunents,  and  tem- 
perature. 

Terrestrial  animals  are  the  most  specialised,  and 


Classification  and  Distribution  of  Animals.  17 

have  organs  in  a  more  concentrated  condition  than  in 
their  aquatic  allies. 

Parasitism. — Some  animals  pass  their  lives  within 
or  on  the  bodies  of  others,  and  this  condition  induces 
striking  alterations  in  structure.  In  some  cases  the 
intruder  collects  its  own  food  independently  of  his 
host,  being  thus  only  indebted  to  him  for  house  room  ; 
of  this  nature  are  the  sponges  which  live  rooted  on 
crabs,  or  the  barnacles  on  the  skin  of  the  whale.  The 
second  series  of  intruders  are  fellow  commoners  with 
their  hosts,  feeding  on  the  food  which  their  entertainer 
collects  ;  while  in  a  third  class  the  parasite  is  a  pen- 
sioner on  the  body  of  his  host,  feeding  on  his  sub- 
stance. Such  forms  are  true  parasites. 

In  all  these  conditions  there  is  a  diminished 
necessity  for  locomotion  and  for  food-capture  on 
the  part  of  the  parasite  ;  so  the  organs  of  motion,  of 
sense,  and  of  nutrition  retrograde,  but  as  the  parasitic 
condition  involves  difficulties  in  the  continuance  of 
the  species,  the  organs  of  multiplication  are  enor- 
mously increased  in  size  and  complexity. 

Extension  in  Time.— Species  of  animals  have 
limited  ranges  in  time  as  well  as  in  space,  for  they 
are  dependent  on  the  constancy  of  physical  conditions 
for  their  specific  longevity,  and  such  alterations  in  these 
as  are  constantly  occurring  will  tend  to  extinguish 
species  ;  hence  the  history  of  life  in  the  past  is  a  con- 
tinual record  of  the  dying  out  of  types  of  life. 


18 


Invtrtebrata. 


CHAPTER   IV. 


SUB-KINGDOM 


PROTOZOA. 


General  Characters. — The  constituent  animals  of  this 
sub-kingdom  are  animals  of  extreme  simplicity,  con- 
sisting for  the  most  part  of  undifferentiated  protoplasm. 
None  of  them  possess  a  nervous  system,  sense  organs, 
nor  a  body  cavity,  nor  do  we  find  differentiated  organs 
present  in  any  of  them. 

Among  these  there  are  five  chief  types  forming  five 
classes. 

FIG.  7. 


One  of  the  minute  Foraminifera,  Globige*  ina  bulloides,  magnified 
seven;  y  diameters. 

Certain  forms,  called  Monera,  are  even  simpler 
than  the  Rhizopods,  as  they  not  only  want  the  power 


Protozoa.  19 

of  house-building  but  have  no  nuclei,  and  are  thus  the 
simplest  conceivable  living  beings,  mere  specks  of 
living  jelly  (fig.  9).  Of  these  naked  forms,  some  authors 
make  a  separate  class  under  the  name  Monera. 

Class  1.  Rhizopoda. — In  the  fine  white  sand  on 
the  sea-shore  or  in  the  mud  of  the  sea-bottom  there  are 
to  be  found  minute  calcareous  shells  of  varying  forms, 
ranging  from  -yj-g-th  to  -j^th  of  an  inch  in  diameter. 
Each  shell  consists  of  many  separate  chambers, 
arranged  either  one  after  another  in  a  straight  line 
or  in  a  single  or  double  spiral,  or  even  grouped  in 
more  complex  fashions.  Each  chamber  is  separated 
from  its  neighbours  by  a  partition  which  is  pierced 
with  one  or  many  holes  whereby  the  several  chambers 
communicate  with  each  other.  The  shell-substance 
is  either  white  and  porcelain-like,  or  glass-like  and 
more  brittle,  and  pierced  not  only  in  the  partitions  but 
over  its  whole  surface  by  numerous  holes.  On  ac- 
count of  these  perforations  these  little  shells  are  called 
Eoraminifera  (hole  bearing). 

The  animals  which  build  these  wonderful  houses 
are  exceedingly  simple  in  their  structure.  The  interior 
of  each  chamber  in  a  fresh  state  is  filled  with  proto- 
plasm which  is  jelly-like,  highly  contractile  on  being 
irritated,  and  not  only  extends  through  the  holes  in 
the  shelly  wall  but  coats  the  outside  of  the  shell  with 
a  glairy  external  living  layer.  This  layer  has  no  defi- 
nite uniformity  of  outline,  but  is  constantly  changing 
its  shape  by  sending  into  the  surrounding  water 
radiating  protoplasmic  processes  which  are  incon- 
stant, rapidly  retracted,  disappearing  by  being  taken 
into  the  homogeneous  matter  of  the  animal's  body, 

C2 


20 


Invertebrata. 


and  coalescing  when  they  touch  each  other.     To  these 
the  name  pseudopodia  (false  feet)  has  been  given. 

These  little  creatures  live  on  any  minute  organic 
particles  with  which  they  come  in  contact,  and  their 
mode  of  feeding  is  simple ;  when  the  ray-like  pseudo- 
podia touch  a  particle  of  which  they  seem  to  approve 
as  a  prospective  meal  they  converge  around  it,  and 

FIG.  8. 


Rotalia.  Veneta,  a  Rhizopod,  showing  the  pseudopodia. 

touching  each  other  coalesce,  and  draw  the  particle 
within  the  body  proper,  in  which  it  is  digested.  As 
these  creatures  are  homogeneous  or  nearly  so,  any 
one  spot  is  as  suitable  for  the  protrusion  of  pseudo- 
podia or  for  the  taking  in  of  food  as  another,  but 
usually  the  processes  are  most  numerous  opposite  the 
holes  in  the  shell. 


Protozoa.  2  1 

As  the  protoplasm  includes  its  food  in  the  manner 
described,  foreign  particles  and  fine  granules  become 
enclosed  in  it  derived  from  the  undigested  parts  of  the 
food.  Sometimes  drops  of  water  or  of  thin  fluid  may 
be  seen  in  the  protoplasm  like  little  bubbles  ;  these 
are  called  vacuoles  (fig.  14),  and  they  with  the  gran- 
ules circulate  actively  in  the  body  mass  ;  obscure  con- 
densed points  or  nuclei  also  exist,  and  the  name  of 
the  class  is  derived  from  the  root-like  spreading  of  the 
pseudopodia. 

Mode  of  Growth  of  Rhizopoda.—  Those  Rhizo- 
pods  that  separate  lime  from  the  sea-water  to  form 
shells,  begin  the  process  while  they  are  young  single 
masses,  and  they  increase  by  budding,  each  bud 
forming  on  the  newest  FIG.  9. 

end  of  the  last  bud  ; 
consequently  the 
perfect  animal  con- 
sists of  a  rod-like  or 
spiral  set  of  chambers, 
each  chamber  being  a 
new,  undetached  bud. 

Two  forms  of   Protozoa.    Protamceba  pri- 
DUOS      DeCOme          mltiva,  the  simplest  living  animal  ;  Mago- 


,          sphtera  planula,  a  compound  form. 

quite  separate  and 
grow  into  new  individuals.  In  a  few  cases  each 
bud  becomes  detached,  so  that  the  animals  always 
remain  of  one  chamber. 

Shell-forming  Rhizopods  are  occasionally  aggre- 
gated in  great  masses  and  sometimes  at  great  depths  in 
the  ocean.  Such  seems  to  have  been  their  habit  in 
past  times,  and  many  of  the  chalky  limestones  consist 
of  the  accumulated  shells  of  Foramimfera. 


Invertebrate. 


Fig.  10. 


Class  2.  Protoplasta.— In  the  slowly  running 
waters  of  ditches,  or  in  bog  pools,  are  found  curious 
creatures  in  many  respects  reminding  us  of  the  naked 
Rhizopods.  These  amoebae  as  they  are  called,  are 
little  masses  of  protoplasm,  moving  and  taking  food 
by  means  of  pseudopodia.  On  close  inspection  many 
particulars  will  be  noticed,  in  which  they  differ  from 
those  simple  creatures  which  we  have  already  ex- 
amined. Thus  their  pseudopodia  are  blunt,  and  do 
not  freely  coalesce,  on  touching  each  other ;  the 
granules  and  vacuoles  are  not  uniformly  distributed 
through  the  protoplasm,  but  are  for  the  most  part  in 
the  central  region,  while  the  outer  protoplasm  is 
firmer.  We  also  notice  a  denser  central  spot  in  the 

body,  to  which  the 
name  nucleus  is  given, 
as  can  be  seen  in  each 
component  mass  of 
Magosphsera  (fig.  9) ; 
and  one  or  more 
little  clear  spaces  may 
be  seen  occasionally 
to  contract  and  ex- 
pand alternately. 
Thus  in  the  group  of 
organisms  of  which 

Heliophrys    variabilts.     One   of   the     Sun  ,          .          , 

animalcules    showing    the    pseudopodia,     am<KOa      IS     the    type, 

nuclei,  vacuoles,  &c.  protoplasm    has    be- 

come  partly  differentiated,  that  is,  some  parts  have 
assumed  characters  which  the  simple  protoplasm 
did  not  possess.  On  account  of  this  first  trace 
of  the  development  of  tissue  we  call  this  group  of 


Protozoa.  23 

animals  Protoplasta  (first  tissue).  The  amount  of 
this  differentiation  is  in  some  scarcely  recognisable, 
while  in  others,  the  sun  animalcules  or  Heliozoa 
(fig.  10),  there  are  many  nuclei,  and  each  of  the  fine 
ray-like  pseudopodia  exhibits  distinctly  an  inner 
axis  of  the  granule-holding  protoplasm  and  an  outer 
layer  of  firmer  material.  These  animals  multiply 
by  division,  and  in  modes  of  feeding,  &c,  they  re- 
semble the  Rhizopods,  with  which  they  are  often 
united. 

Class  3.  GregarinaB.  —  A  group  of  curious  parasites, 
the  Grtgaritta,  manifest  a  similar  process  of  differentia- 
tion taking  place  in  their  life-history. 
These  minute  creatures  are  found  in 
the  digestive  canals  of  beetles,  earth- 
worms, &c.,  and  in  their  mature  states 
they  appear  as  elongated  bodies  with 
a  firm  outer  wall  which  never  be- 
comes protruded,  and  consequently 
does  not  allow  of  the  formation  of 
pseudopodia  (fig.  i,  A,  B).  This 
outer  stratum  may  itself  consist  of  A.  Gregarine  f.om  the 
two  layers;  while  internally  the 
protoplasm  contains  a  solid  nucleus. 
At  a  certain  stage  in  its  existence  ™becuia. 

P  c.  Boat-shaped      body 

the  adult  Greganne  becomes  almost 


...  .  ,  D.  Amaebiform      body 

globular  and  quiescent,  loses  its  set  free  from  Pseudo- 
nucleus,  and  its  internal  material 
becomes  aggregated  into  many  boat-  shaped  bodies, 
contained  within  the  firm  outer  layer  through  which 
they  eventually  burst  ;  each  of  these  boat-like  bod-.es 
(fig.  nc)  consists  of  a  rigid  outer  case  and  an  inner 


24  Invertebrata. 

particle  of  protoplasm.  The  former  soon  gives  way, 
and  the  inner  portion,  freed  from  external  restraints, 
moves  actively  by  pseudopodia  like  a  Rhizopod  (fig. 
n,  D).  On  reaching  a  suitable  nest  this  amceboid 
particle  undergoes  further  development,  and  becomes 
a  Gregarine  like  its  parent  In  size  these  parasites 
range  from  the  ^Vth  to  f  rds  of  an  inch. 

Class  4.  Radiolaria. — On  examining  the  material 
brought  up  from  ocean  bottoms,  there  are  frequently 
found  small  and  beautifully  sculptured  shells,  differing 
from  those  of  the  Foraminifera  in  that  they  consist 
of  silica,  not  of  lime,  and   hence  they  are  compara- 
tively indestructible  by  maceration  in 
acids,  by  which  process  they  can  be 
isolated  from  the  mud  wherein  they  are 
found.      In  pattern    these   shells  fre- 
quently consist  of  symmetrical,  radia- 
ting rods,  united  by  a  variously  patterned 
interweaving  of  threads  of  silica,  the 
whole  making  a  network  often  resem- 
bling flower-baskets,  disks,  and  perfor- 
ated spheres,  hour-glasses,  or  helmets. 
The    animals    which    form    these 
exquisitely  ornate  little  shells  are  found 
to   be   comparatively   simple,   and    in 
many  respects  allied  to  the  Rhizopods, 
shell  of  a  as  tney  send  out  fine  thread-like  pseu- 
T  dopodia,  from  the  surface  layer.     The 
deeper  protoplasm   is    enclosed  in  a 
central  membranous   capsule,  perforated  with  holes, 
and  it  contains  fat,  cellular  masses,  pigment  and  often 
a  central  vesicle  or  sac  with  striped  walls;  curious 


Protozoa. 


yellow  cells  are  found  scattered  through  the  body  in 
almost  all  species. 

In  size  these  Radiolarians  are  from  \  to  -gj^th  of 
an  inch  in  diameter,  the  larger  forms,  however,  are 
not  single  individuals  but  clusters  united  into  compact 
colonies,  each  component  individual  having  its  own 
central  capsule.  Most  of  these  are  found  floating  on 
or  in  the  waters  of  the  sea.  Some  oceanic  forms  have 
no  skeleton,  and  are  described  under  the  name  sea- 
glue  (Thatassicolla). 

Some  allied  forms,  destitute  of  central  capsule  and 
of  yellow  cells,  are  found  in  fresh- water  bog  pools  in 
this  country. 

CHAPTER  V. 

SUB-KINGDOM  i  :  PROTOZOA — continued. 

Class  5.  Infusoria. — If  we  place  under  the  micro- 
scope, water  in  which  animal  or  vegetable  matter  has 
been  infused  for  six  cr 
seven  days,  especially  in 
warm  weather,  we  see  that 
the  fluid  contains  minute, 
actively  moving  creatures 
ranging  in  size  from  ^Vtri 
to  the  T^Vfrth  of  an  inch 
in  length.  They  are 
mostly  oblong  in  shape 
and  their  rapid  locomo- 
tion is  due  to  the  action 

c  f-  .,          .,        ...         ,•    v  Three  Ciliated  Infusoria. 

Of  fine  Vlbratlle  Cilia  which    A>  Oxytrichaf>ibba.  B.  Trachelocerca 

clothe,   either   the  whole        bice*s-  c-  Vorticella'  citrin«- 


FIG.  13. 


26  Invcrtebrata. 

surface;  or  else  special  areas  of  it ;  sometimes  a  few  of 
these  processes  are  rigid  and  act  like  little  feet,  or 
else  they  are  all  equal  and  fine,  invisible  during  their 
active  exercise  owing  to  their  rapid  rate  of  motion. 

The  outer  layer  of  their  body  is  a  firm  cuticle 
which  covers  a  differentiated  protoplasmic  lamina  con- 

FIG.  14. 


Paramcecium  aurelia,  an  infusorian,  showing  the  contractile  vesicles  (i')» 
cilia  and  vacuoles  (a). 

taining  one  or  more  clear  spaces  or  contractile  vesicles, 
which  when  watched  can  be  seen  to  expand  and  con- 
tract regularly,  pulsating  like  a  heart.  Within  this  layer 
is  a  more  fluid  mobile  protoplasm  containing  granules, 
vacuoles  and  a  pair  of  singular  solid  bodies  called  re- 
spectively nucleus  and  nucleolus. 


Protozoa.  27 

Near  one  end  of  the  body  there  is  usually  a  funnel- 
shaped  mouth  opening  into  the  inner  protoplasm, 
where  digestion  takes  place,  as  in  Rhizopods ;  the  un- 
digested particles  are  ejected  at  a  spot  where  the  outer 
wall  seems  deficient,  and  which  sometimes  is  a  distinct 
opening. 

These  animals  multiply  either  by  fission  like  most 
of  the  other  Protozoa,  or  else  the  nucleus  breaks  up 
into  egg-like  masses  which  seem  to  develop  into  new 
infusoria.  This  condition  is  preceded  by  the  forma- 
tion of  a  mucous  mass  around  the  animalcule,  which 
becomes  quiescent,  losing  its  cilia. 

The  Vorticella,  or  bell  animalcule  (Fig.  13,  c)  is  a 
common  form  fixed  by  a  slender  footstalk,  which  on 

FIG.  15. 


Noctiluca  miliaris,  a  marine  luminous  Atineta  mystacina* 

animacule.  showing  its  flagellum. 

irritation  instantly  contracts  into  a  spring-like  spiral 
and  the  ciliary  crown  around  the  mouth  of  the  bell 
becomes  introverted.  Another  common  form,  Ophry- 
dium,  has  an  outer  gelatinous  envelope,  and  as  division 
proceeds,  this  keeps  the  broods  together  so  that  they 


28  Invertebrata. 

sometimes  form  masses  of  more  than  an  inch  in 
diameter,  which  ay^  often  found  floating  on  standing 
water.  The  commonest  forms  are  the  slipper  animal- 
cule (fig.  14),  the  boat-like  animalcule  or  Evplotes  (fig. 
i),  and  the  hay  infusion  animal  or  Colpoda,  but  almost 
every  infusion  has  its  own  form  of  animal. 

Several  groups  of  microscopic  animals  are  allied  to 
the  Infusoria.  Some  of  these  are  called  monads  and 
are  mouthless  nucleated  bodies  with  one  long  cilium. 
Another  of  these  is  Noctiluca  (fig.  15),  a  globular 
creature  about  ^th  of  an  inch  long,  with  a  short  obtuse 
vibrating  flagdlum  or  filament  and  a  mouth,  but 
whose  interior  consists  of  netted  protoplasmic  threads 
whose  meshes  are  filled  with  water.  These  organisms 
are  among  the  commonest  of  those  to  which  the  sea 
owes  its  phosphorescence. 

Other  minute  forms,  called  Acinetse  (fig.  16),  are 
small,  stalked  masses  whose  surface  is  studded  with 
radiating,  retractile  tubular  suckers,  through  which 
they  suck  the  juices  of  their  prey. 


CHAPTER  VI. 

SUE-KINGDOM    II  :    SPONGES    (POLYSTOMATA). 

Metazoa. — All  animals  above  the  Protozoa  possess 
an  internal  body-cavity,  the  wall  around  which  is 
made  up  of  three  primary  layers,  often  with  difficulty 
discriminable  in  the  lowest  forms  ;  and  there  is  either 
one  terminal  mouth  into  the  cavity,  or,  as  in  the  case  of 
the  sponges,  many  lateral  pores  communicate  there- 
with. 


Polystomata. 


29 


Characters  of  Sponges. — The  common  toilet 
sponge  is  a  representative  of  a  group  of  animals 
whose  affinities  are  not  easily  understood.  On  ex- 
amination with  a  magnifying  glass  it  will  be  found  to 
consist  of  irregularly  branching  and  re-uniting  threads 
of  a  highly  elastic  material,  so  arranged  that  the  inter- 
spaces between  the  finer  branches  appear  as  pores  or 
canals,  which,  from  the  nature  of  their  walls,  freely 
communicate  with  each  other. 

On  examining  the  surface  of  a  sponge,  some  large 
holes  will  be  seen,  which,  on  being  cut  into,  are  found 
to  be  the  extremities  of  wide  FIG.  17. 

spaces  or  tubes  ;  these  divide 
within  the  sponge-mass  into 
smaller  canals,  which  again  divide 
and  subdivide  until  finally  they 
end  in  the  fine  canals  whose 
terminations  are  the  minute  sur- 
face pores  between  the  superficial 
fibres  of  the  mass.  The  walls  of 
these  spaces  are  themselves  full 
of  small  pores  in  the  interstices  of 
the  fibres  which  form  the  sub- 
stance. This  horny  mass  is  really 
the  sponge  skeleton,  having  the 
same  relation  to  the  sponge 
animal  that  the  spicules  of  Radio-  A  calcareous  sponge, 
larians  bear  to  the  soft  parts  of  those  creatures. 

We  can  most  easily  understand  the  nature  of  a 
sponge  animal  by  examining  such  simple  forms  of  the 
group  as  may  be  found  encrusting  sea-weeds  or  stones 
on  our  own  shores.  These  are  nearly  cylindrical, 


3O  Invertebrata. 

rooted  by  a  flat  protoplasmic  expansion  below  (fig. 
17),  and  have  a  single  wide  opening  above,  which 
is  named  the  osculum.  Its  walls  are  pierced  by 
numerous  fine  apertures  or  pores,  which  open  di- 
rectly into  the  central  cavity.  The  wall  consists  of  a 
cluster  of  Monad-like  cells,  provided  with  a  collar, 
each  sending  out  a  pseudopod.  In  the  wall  and 
around  each  of  the  lateral  pores  are  needle-like 
spicules  of  carbonate  of  lime  usually  united  in  threes, 
and  arranged  in  a  radiated  manner.  Sometimes  they 
are  in  pairs  or  in  twos.  Others  are  like  anchors,  with 
two  flukes. 

As  in  most  sponges  the  wall  of  the  body-cavity 
below  each  mouth  is  thick,  not  simple  and  membranous, 
the  pores  elongate  into  canals.  Most  sponges  also 
grow  in  tufts  or  clusters  arranged  so  close  together 
that  the  outer  pores  of  the  neighbouring,  and  closely 
united  animals  communicate  with  each  other  ;  thus  a 
complex  canal  system  grows  up,  according  to  the 
degree  of  thickening  of  the  wall  and  coalescence  of 
separate  elements  of  the  clusters,  as  well  as  by  the 
superaddition  of  interspaces,  which  are  often  branched, 
between  the  separate  individuals  or  elements. 

In  a  living  sponge,  currents  of  fluid  set  in  through 
the  minute  pores  on  the  surface,  setting  out  in  large 
streams  through  the  oscula  ;  thus  there  are  many 
mouths  and  few  outlets.  These  currents  are  kept  up 
by  the  waving  of  the  flagella  which  bedeck  the  pro- 
toplasm masses  that  line  the  canals  and  cover  the 
skeleton,  and  as  these  currents  traverse  the  canals  the 
small  organic  particles  which  they  carry  in  are  taken 
up  by  the  cells  of  the  wall  in  the  same  manner  as  food 
particles  are  swallowed  by  Rhizopods. 


Polystomata.  3 1 

Spicules. — The  skeleton  of  most  sponges  consists 
not  only  of  the  horny  material  with  which  we  are  familiar 
in  the  toilet  sponge,  but  ofspicules  of  silica  of  various 
shapes  embedded  in  the  horny  mass,  resembling  pins, 
needles,  clubs,  crosses,  anchors,  hooks,  wheels,  &c.  In 
others,  siliceous  spicules  alone  make  up  the  skeleton, 
which  has  no  horny  matter.  There  is  a  calcareous 
skeleton  in  another  group. 

Reproduction  and  Classification.  —  Sponges 
multiply  by  division,  either  natural  or  artificial. 
That  is,  if  we  cut  up  a  living  sponge  into  many  small 
pieces,  each  can  grow  into  a  perfect  sponge!  Other 
modes  of  growth  or  reproduction  are  by  contin- 
uous budding,  by  the  formation  of  free  buds,  usually 
arising  in  autumn  and  growing  in  the  ensuing  spring, 
or  else  by  the  formation  of  eggs  which  have  been 
found  in  summer  in  many  forms,  and  which  develop  in 
the  following  year  Sponges  are  classified  according 
to  the  material  of  the  skeleton  and  the  shapes  of  the 
spicules.  Thus  there  are  calcareous,  horny,  and 
siliceous  sponges.  The  last  class  is  the  largest  and 
includes  some  remarkable  forms,  such  as  the .  boring 
sponge  (Cliona  celata),  which  pierces  holes  in  old 
oyster  shells  on  our  sea-shore,  and  is  known  by  its  pin- 
shaped  spicules.  The  remarkable  Neptune's  cup 
(Raphwphora)  is  closely  allied,  though  very  dissimilar 
in  shape  and  size.  Hyaloncma,  the  glass-  tope,  from 
Japan  and  Portugal,  has  long  twisted  siliceous  spicules. 
Etipleetella,  the  exquisite  Venus's  flower-basket,  from 
the  Philippines,  is  now  well  known  as  an  ornament, 
and  exhibits  .1  most  wonderful  interweaving  of  siliceous 
spicules.  Sj>ongi<!a,  the  common  green  fresh-water 


32  In  vertebrata. 

sponge  of  lakes  and  rivers,  is  a  familiar  form,  and  each 
autumn  it  will  be  found  to  display  the  formation  of 
winter  gemmules  or  free  buds.  Halichondria  (Chali- 
nula)  is  the  common  sponge  found  on  our  sea  shores, 
and  Sycandra  is  the  compressed  white  calcareous 
sponge  found  pendulous  from  rocks,  or  adhering  to 
sea-weed  near  low-water  mark. 


CHAPTER   VII. 

SUB-KINGDOM    III  :       CCELENTERATA.       CLASS    I. 
HYDROZOA,    JELLY-FISHES. 

General  Characters  of  Hydra. — The  common  Hydra 
(figs.  2  and  1 8),  an  inhabitant  of  our  stagnant  pools, 
is  the  type  of  the  third  sub-kingdom  of  animals.  This 
voracious  creature  rarely  exceeds  half 
an  inch  in  length,  and  possesses  a  cy- 
drical  body  having  the  mouth  at  one 
end  and  a  sucking  disk  for  voluntary 
attachment  at  the  other.  Around  the 
mouth  are  six,  seven,  or  even  ten 
slender  contractile  arms,  capable  of 
rapid  motion,  and  about  as  long  as 
the  body,  or  even  longer  ;  these  can 
be  seen  actively  engaged  in  seizing 
Hydra  a^Ztaca.  prev  and  dragging  it  into  the  central 

the  orange  hydra,     1       J 

showing  its  tenta-    mouth  (fig.  1 8  T).     The  body  is  com- 

clesandreproduc-  ' 

tive  organs.  posed  of  two    membranes,   an   outer 

and  an  inner;  the  former,  which  is  called  ectoderm 
(outer  skin),  making  up  the  whole  outer  surface,  the 
latter  (called  endoderm  or  inner  skin)  lining  the  interior 


Hydra. 


33 


of  the  body,  which  consists  of  a  simple  stomach 
cavity  from  which  the  effete  matters  are  ejected  by 
the  mouth. 

On  watching  the  process  of  feeding  we  notice  that 
the  arms  exercise  a  power  over  living  prey  far  greater 
than  we  could  anticipate  from  their  size ;  and  on 
close  inspection  these  tentacles  (as  the  arms  are  called) 
are  seen  to  be  covered  with  minute  oval  sacs,  whose 
outer  thin  walls  (fig.  19  B),  are  easily  burst  by  pres- 
sure, and  when  this  occurs  a  long  whiplash-like 
filament  (c)  which  lay  coiled  within  the  cell,  is 
suddenly  projected,  thus  ren- 
dering the  tentacle  a  formidable 
organ  for  seizing  prey,  their  action 
being  either  mechanical,  or  by 
virtue,  possibly,  of  some  poisonous 
fluid. 

The  cells  of  the  outer  layer  in 
Hydra  have,  projecting  inwards  or 
towards  the  endoderm,  slender 
thread-like  contractile  processes, 
acting  like  muscular  fibres.  The 
ectodermal  cells  resemble  nerve  A, 
cells,  and  hence  to  this  stratum  the 
name  neuro-muscular  cell-layer  is 
given. 

Reproduction.  —  Hydras  in 
early  summer  send  off  from  near  the  base  of  the  body 
small  buds  (fig.  2),  which  grow  rapidly,  each  deve- 
loping a  mouth  at  its  free  end,  together  with  a  crown 
of  tentacles,  then,  being  detached,  it  assumes  a  sepa- 
rate existence.  Sometimes  a  second  crop  of  buds 

D 


Planula  or  earliest 
stage  of  a  hydroidonits 
emission  from  the  egg. 
B,  Thread-cell  undis- 
turbed. C,  the  same 
with  the  filament  pro- 
truded. 


34 


Invertebrata. 


arises  from  the  first  bud  before  it  has  detached  itself 
from  its  parent. 

Later  on  in  the  season,  eggs  form  within  the  Hydra, 
beginning  as  modified  cells  of  the  inner  layer.     These 


FIG.  20. 


\ 


Sert-ularia  alietina,  one  of  the  sea-firs  ;  a  natural  size,  b  magnified.     The 
figure  shows  the  stem,  or  ccenosarc  of  the  colony,  with  its  polypites. 

burst  through  the  surface  (fig.  18,  d),  become  free,  and 
in  spring  they  shed  their  outer  layer  and  proceed  to 
develop  into  new  Hydrae,  which  in  course  of  time  give 
rise  to  buds. 

Sub-Class  1 :  Hydroida. — All  the  lower  coelenterate 
animals  are  built  on  the  pattern  of  the  hydra,  they 


Jelly  fishes.  35 

only  differ  in  the  details  of  their  organisation  and 
arrangement.  In  many  of  the  marine  forms,  the 
hydra-like  animals  are  grouped  in  clusters  or  colonies 
on  a  branched  common  axis  or  stalk  (fig.  20).  In 
each  of  these  colonies  every  hydra-like  organism  is 
called  a  polypite,  and  the  common  stalk  of  the  colony 
is  called  the  ccenosarc. 

These  colonies  we  find  on  the  sea-shore  as  branch- 
ing tree-like  growths  on  sea-weeds,  often  exceeding  six 
inches  in  length,  and  some  of  them  are  known  as  *  sea- 
firs.'  Each  group  begins  its  existence  as  a  single  poly- 
pite,  rooted  by  that  extremity  of  its  body  which  is  oppo- 
site to  the  mouth.  From  this  root  a  stalk  of  ccenosarc 
grows  upwards,  and  on  this  stalk  new  polypites  form, 
each  like  a  hydra  in  structure.  New  polypites  arise  as 
outgrowths  from,  and  are  structurally  continuous  with 
the  common  stem  of  the  colony ;  and  so  the  stomach 
of  each  is  continuous  with  the  tubular  centre  of  the 
stalk.  On  this  account  there  is  a  community  of  nutri- 
tion in  the  colony,  a  few  actively-feeding  polypites 
being  able  to  make  up  for  the  laziness  of  others,  which 
participate  in  the  nourishment  taken  in  by  their  more 
active  neighbours. 

Medusoids. — In  these  colonies  some  polypites  are 
set  apart  for  the  production  of  eggs  for  the  multiplica- 
tion of  individuals  (fig.  21,  c,  D).  Such  polypites  are 
much  altered  in  form,  and  they  frequently  become 
detached  from  the  stem  and  float  about  freely  often 
as  little  jellyfishes  about  the  size  of  a  pea ;  they  are 
called  medusoids.  With  a  fine  muslin  surface-net  in 
any  of  our  seas,  many  forms  of  these  little  creatures 
may  be  captured,  especially  in  summer  or  autumn; 
D  2 


36  Invertebrata. 

each  appears   somewhat    umbrella-shaped,    and   the 
margin  of  its  disk  or  swimming  bell  is  adorned  with 

FIG.  2t. 


Different  stages  of  Medusoids  :  A,  rooted  hydroid  colony,  natural  size  ;  B, 
polypite  magnified,  showing  tentacles  and  swimming  bells  ;  c,  D   repro- 
ductive swimming  bells,  detached  and  free-swimming. 

little,  naked,  coloured  specks  supposed  to  be  eyes, 
and  also  with  marginal  tentacles.  A  central  mouth 
exists  on  the  under  side  of  the  swimming  bell,  opening 


Growth  of  Hydroid  Colonies. 


37 


into  a  stomach,  from  which  four  tubes  radiate  to  the 
margin  of  the  bell,  where  they  are  united  by  a  circular 


FIG.  22. 


Physalia  or  Portuguese  Man  of  Wai  :  a,  6,  c,  three  stages  of  growth  ;  a',  air- 
sac  or  float  ;  ir  polypites,  T  tentacles. 

canal,  in  the  walls  of  which,  or  within  the  wall  of  the 
stomach,  the  eggs  are  formed 


38  Invertebrata. 

Unlike  as  this  jellyfish  may  appear  to  be  to  Hydra, 
it  is  in  reality  a  polypite  modified  by  a  widening  and 
thickening  of  the  body  wall  at  the  base  of  the  tenta- 
cles, and  an  elongation  of  the  mouth  into  a  central  stalk. 
These  free-swimming  jellyfishes  are  thus  not  distinct 
animals,  but  only  detached  parts  of  hydroid  colonies, 
and  the  eggs  produced  by  them  first  give  origin 
to  small  ciliated,  infusorium-like  bodies  (p.  25), 
called  planulae  (fig.  19,  A)  which  after  a  short  period 
of  freedom  settle  on  stones  or  shells  at  the  sea-bottom, 
and  develop  into  primary  polypites  and  the  common 
stem  of  a  new  colony,  from  which  some  buds  be- 
coming specialised  and  detached  form  in  turn  medu- 
soids.  There  is  thus  an  alternation  of  generations,  the 
progeny  of  the  egg  resembling,  not  the  immediate  egg- 
producer,  but  the  form  which  preceded  this. 

Divisions  of  Hydroida. — Of  fixed  Hydroids  there 
are  three  orders  :  i.  simple  forms,  such  as  Hydra  ; 
2.  compound  colonies  whose  stalks,  polypites,  and 
medusoids  are  naked  (fig.  2 1 ) ;  3.  compound  colonies 
whose  stalks  and  polypites  are  covered  with  a  horny 
casing  as  in  the  true  sea-firs  (Sertularia,  fig.  20). 

Sub-Class  2  :  Siphonophora.  —Floating  on  the  sea 
there  are  frequently  found  colonies  of  hydroid  poly- 
pites, not  unlike  those  of  the  sea-firs  in  structure,  but 
whose  common  stem  instead  of  being  rooted,  swims 
by  means  of  enlarged  and  altered  polypites,  whose 
stomachs  are  undeveloped,  and  whose  bodies  are 
dilated  into  swimming  bells.  From  these,  the  ccenosarc 
extends,  supporting  both  the  nutritive  and  the  repro- 
ductive polypites.  Some  possess  in  addition  a  sac 
filled  with  air  which  acts  as  a  float  and  aids  the 


JettyfisJies. 


39 


swimming  bell  in  locomotion.  This  is  seen  in  the 
Portuguese  Man  of  War  (fig.  22),  whose  purple  crested 
air  sac  and  long  tentacles  are  well  known  to  sailors,  and 
which,  by  their  large  thread-cells,  inflict  dangerous 
stings  on  those  who  incautiously  touch  them.  These 


FIG.  23. 


a 


Disk-bearing  Jelly-fishes ;  a,  Rhizostoma  ;  b,  Chrysaora. 

swimming  and  floating   colonial  Hydroids  are  called 
Siphon-bearers  {Siphonophora). 

Sub-Class  3  :  Discophora. — The  large  jellyfishes 
whose  translucent  bodies  are  so  often  thrown  on  the 
shore  by  the  receding  tides,  are  the  representatives  of 
a  sub-class  characterised  by  possessing  single  polypiteb 


40 


Invertebraia. 


depending  from  the  centre  of  a  large  disk  or  umbrella 
varying  from  an  inch  to  three  feet  in  diameter.  The 
mouth  of  the  polypite  is  surrounded  by  lobate  tenta- 
cles (fig.  24),  and  from  the  stomach  there  pass  eight 
or  more  branching  radial  canals  which  are  united 
peripherally  by  a  circular  canal.  The  eggs  are  pro- 
duced in  pouches  of  the  stomach-cavity,  and  each  of 
these  on  ripening  emits  a  ciliated  germ  like  an  infu- 
sorium (fig.  24  b\  which  after  a  brief  locomotory 
existence  settles  down  on  some  solid  body  at  the  sea 
bottom  (c\  and  develops  a  hydra-like  animal  with 

FIG.  24. 


Medusa  aurita  in  different  stages  of  life  ;  a  perfect  adult  form  reduced  ^  ; 
b,  c,  d  hydra-like  stage;  e,_f  strobila  stages  ;  g  one  of  the  disks  separated 
from./;  and  growing  into  adult  form. 

branching  canals  which,  elongating,  forms  a  little 
rooted  colony  (//).  Each  of  these  hydra-like  forms 
becomes  marked  with  transverse  furrows  (e)  which, 
deepening,  dip  into  the  interior  of  the  body  dividing 
it  into  a  vertical  'pile  of  saucers/  of  which  each  dis- 
coidal  segment  becomes  free  as  a  new  medusa.  This 
is  a  good  example  of  alternate  generations. 


Jelly  fishes  and  A  nemones.  4 1 

In  the  common  Medusa  aurita,  whose  disk  can 
easily  be  recognised  by  the  four,  ring-like,  violet  ovaries, 
there  are  marginal  tentacles  and  also  little  pigment 
spots  and  clear  vesicles  (eyes  and  ears)  symmetrically 
disposed  around  the  disk,  each  covered  by  a  little 
lobe  of  the  umbrella  margin.  There  is  no  trace  of  d 
marginal  membrane  or  veil,  such  as  exists  around  the 
mouth  of  the  bell  of  hydroid  medusae. 

Thread  Cells  and  Nervous  System. — The  stinging 
power  of  these  *  sea  nettles '  is  due  to  their  armature 
of  thread  cells. 

When  a  hydroid  is  cut  in  pieces,  each  piece  be- 
comes a  perfect  animal  if  a  portion  of  the  margin  is 
preserved,  but  if  not,  reproduction  is  very  uncertain. 

In  these  medusoids  we  meet  for  the  first  time 
with  an  area  of  sensitive  tissue  acting  like  a  nervous 
system,  and  connected  with  the  margin  of  the  disk. 
If  this  be  preserved  motion  continues  to  take  place, 
whereas  if  the  margin  be  cut  away  motion  ceases. 

Many  medusae  are  phosphorescent,  emitting  light 
from  the  -^hole  surface,  especially  from  the  margin  of 
the  disk. 

Ctenophora. — In  one  interesting  little  group,a  fourth 
sub-class,  called  Ctenophora,  there  are  eight  radial  rows 
of  comb-like  plates  armed  with  cilia,  which  act  as  rowing 
organs.  In  these  there  is  a  certain  amount  of  bilateral 
symmetry. 

Summary. — The  Hydrae  and  jellyfishes  which 
constitute  the  class  Hydrozoa  possess  a  central 
stomach  cavity  into  which  a  single  aperture  of  entrance 
leads.  They  are  also  armed  with  thread-cells  and 
possess  a  body  wall  of  two  layers. 


Invertebrates 


FIG.  25. 


CHAPTER  VIII. 

ACTINOZOA.    SUB-CLASS  I.   ZOANTHARIA  :   SEA 
ANEMONES. 

Structure  of  a  Sea  Anemone. — In  many  of  the 
rock-pools  around  our  shores  there  are  to  be  found 
the  exquisite  forms  which  are  the  types  of  this 
class,  and  which,  like  animated  flowers,  may  be 
seen  expanding  their  sensitive  petal-like  tentacles 
in  search  of  the  materials  that  constitute  their  prey. 
On  the  retreat  of  the  tide  those  that  are  left  un- 
covered by  the  water  contract,  and  appear  as  little, 
rounded,  firm,  gelatinous  masses,  attached  to  rocks 
and  stones  by  means  of  a  flat  suctorial  disk. 

The  body  of  one  of 
these  when  expanded  is 
somewhat  cylindrical,  hav- 
ing a  free  extremity  which 
bears  the  mouth,  and  an 
attached  end,  which  is 
usually  capable  of  volun- 
tary detachment.  This 
extremity  is  sometimes 
called  the  foot.  On  mak- 
ing a  transverse  section 
the  body  appears^  like  a 
double  tube ;  the  outer 
tube  is  the  body  wall,  the 
inner  bounds  the  stomach, 
and  between  them  is  the  body  cavity  into  which  the 
stomach-sac  opens  below  by  a  narrow  aperture. 


Vertical  section  of  common  Sea  ane- 
mone, Actinia  mesembryanthe- 
mnm. 

•m  mouth,  tnf  primary  mesentery 
iti1  secondary  mesentery,  e  ecto- 
derm, e1  endoderm,  /  tentacle,  t', 
ovary,  d  disc  of  attachment,  s 
body-cavity. 


Sea  Anemones.  43 

The  body-cavity  extends  upwards  into  the  hollow 
tentacles,  each  of  which  is  in  fact  a  tubular  prolonga- 
tion continuous  with  this  cavity.  In  life,  when  the 
body  is  expanded,  the  space  between  the  stomach  and 
the  body  wall  contains  sea-water  which  also  inflates 
the  tentacles,  but  on  irritation  the  contraction  of  the 
outer  wall  drives  out  this  fluid,  which  escapes  in  minute 
jets  through  the  terminal  pores  at  the  extremities  of 
the  tentacles. 

The  body  cavity  is  divided  by  vertical  partitions 
which  pass  inwards  to  the  outside  of  the  stomach- wall, 
and  thus  divide  the  outer  chamber  into  a  series  of 
smaller  compartments  which  radially  surround  the 
stomach,  below  which  they  all  communicate  with 
each  other.  There  are  five  or  six  such  large  partitions 
extending  for  the  whole  length  of  the  body  wall, 
•which  are  called  primary  mesenteries \  and  between 
them  are  smaller  partitions  in  equal  numbers,  called 
secondary  mesenteries,  between  these,  there  are  often 
still  smaller  tertiary  mesenteries,  twice  the  number  of 
the  primaries,  and  in  some  related  forms  other  orders 
of  intermediate  partitions  exist,  still  farther  sub-divid- 
ing the  body  cavity,  but  each  set  shorter  than  its  pre- 
decessors. 

The  outer  surface  of  a  sea  anemone,  and  especially 
of  the  tentacles,  is  richly  covered  with  thread  cells, 
which,  when  burst,  are  sometimes  thrown  off  as  a 
continuous  slough.  This  can  be  seen  when  an  ane- 
mone is  imprisoned  in  a  bottle  of  sea-water,  and  in 
the  same  condition  we  notice  that  as  the  water  be- 
comes less  able  to  support  the  life  of  the  creature 
from  its  loss  of  oxygen  and  of  material  for  food,  that 


44  Invertebrata. 

the  body  becomes  enormously  swollen  by  the  inordi- 
nate amount  of  water  which  the  anemone  takes  in. 

Multiplication.  —  Sea  anemones  occasionally 
multiply  by  division,  but,  in  general  they  increase 
by  the  development  of  eggs,  in  the  thick  cord -like 
edges  of  the  mesenteries.  These  eggs  are  emitted 
by  the  mouth,  and  from  them  arise  minute,  ciliated 
embryos  which  become  saccular. 

Anemones  can  be  multiplied  also  by  artificial  divi- 
sion, and  if  an  anemone  be  cut  horizontally  the 
mouth  end  still  continues  to  eat,  and  finally  develops 

FIG.  26. 


CaryophyUia  fascicttlata,  a  sclerodermic  coral.  The  Jeft  side  of  the  figure 
shows  the  coral  denuded  of  soft  parts  ;  on  the  right  the  animal  matter  is 
shown,  while  at  the  upper  part  several  of  the  polypes  are  seen  projecting. 

a  foot,  while  the  foot  end  may  (but  seldom  does)  con- 
tinue to  live  and  may  ultimately  develop  tentacles. 
One  experimenter  produced  by  his  sections  an  ane- 
mone with  a  tentacle-armed  mouth  at  each  end. 
Corals  and  Coral  Building. — Most  sea  anemones 


Coral  Builders.  45 

are  solitary  ;  a  few  only  form  colonies  by  continuous 
budding,  and  by  the  formation  of  a  uniting  ccenosarc. 
In  sea  anemones  proper,  there  is  no  deposition  of  an 
indurating  material,  but  in  tropical  seas  a  closely 
allied  group  of  animals  abstract  lime  from  the  sea- 
water,  and  lay  it  down  in  one  of  two  ways,  either  in 
the  animal's  tissues,  or  else  in  the  centre  of  the 
ccenosarc,  and  aroimd  the  body,  outside  the  foot  of 
each  separate  polyp.  Hard  masses  thus  formed 
are  called  corals  ;  and  all  the  reef-building  corals,  the 
Madrepores  and  Oculinas,  are  examples  of  the  former 
kind,  or  tissue-depositions.  The  deposit  may  be 
in  the  body  wall,  in  the  mesenteries  of  the  polyps, 
or  in  the  ccenosarc.  Growth  in  these  colonial  forms 
takes  place  either  by  the  formation  of  buds  which 
remain  continuous  and  may  spring  from  various 
parts  of  the  original  stem,  or  else  by  fission,  but  in 
this  case  the  new  polyps  remain  connected  together. 
Owing  to  these  different  modes  of  growth  there 
is  much  variety  of  shape  and  structure  among  the 
hard  parts  of  different  corals.  Large  masses  of  coral, 
which  are  called  reefs,  are  usually  found  in  the  seas 
of  such  climates  as  have  a  winter  average  tem- 
perature over  60°  F.  and  where  the  water  is  clear, 
and  not  mixed  with  mud  or  fresh  water.  They 
abound  chiefly  between  the  depths  of  i  and  50 
fathoms,  and  vary  in  form  according  to  the  shape  and 
condition  of  the  sea-bottom. 

A  few  of  the  coral-building  animals  are  solitary, 
like  the  little  Caryophyllia  of  European  seas.  Some 
of  the  commonest  forms  of  corals  brought  to  this 
country  from  the  tropics  are  the  mushroom-shaped 


46  Irwrtebrata. 

lamellar  Fungia,  the  richly  perforated  Madrepores,  and 
the  brain-corals,  or  Af&andrina. 

Sub- Class  2,  Alcyonaria. — The  sea  often  casts  on 
the  shore  large,  yellowish,  gristly  masses,  known  by 
the  fishermen  as  '  dead  men's  fingers/  but  technically 
named  Alcyonium,  which  are  types  of  the  second  sub- 
class of  Actinozoa.  On  placing  this  Alcyonium  in  sea- 
water  the  surface  sends  forth  from  each  pore  a  little 
crown  of  tentacles.  These  are  seen  to  be  in  circlets 
around  the  mouths  of  minute  polyps,  and  they  differ 
from  the  tentacles  of  sea-anemones  in  two  respects ; 
first,  they  are  in  multiples  of  four,  usually  being  eight 
in  number,  and,  secondly,  they  are  pinnately  fringed, 
that  is,  evenly  toothed  and  lobed  around  the  margin, 
each  little  tooth  having  a  hole  at  its  tip :  otherwise 
the  organisation  is  of  the  same  type  as  that  of  a  sea 
anemone.  Minute  calcareous  spicules  are  abundantly 
scattered  through  the  mass,  and  in  some  allied  forms, 
these,  together  with  hard  horny  matter,  make  up  a  con- 
tinuous, coral-like,  foot- secretion  in  the  axis  of  the 
ccenosarc,  as  in  the  fan-corals  or  Gorgonias.  In  the 
precious  red  coral  of  the  Mediterranean,  this  axis  is 
of  stony  hardness  ;  and  in  Jsis,  calcareous  and  horny 
joints  alternate  with  each  other  in  the  central  axis  of 
the  stem,  thus  combining  firmness  and  flexibility. 
The  red  organ-pipe  coral  of  the  Indian  Ocean,  with  its 
table-like  partitions  and  its  green  polyps,  belongs  also 
to  this  group.  The  feather-shaped  sea-pens,  which 
are  nearly  related  to  the  Gorgoniae,  are  not  rooted, 
but  have  the  extremities  of  their  stems  buried  in  sand. 

Recapitulation. — All  the  animals  which  make  up 
the  sub-kingdom  Coelenterata  show  a  radiated  arrange- 


Echinodermata.  47 

ment  of  parts,  the  bodies  being  formed  of  a  series 
of  symmetrical  segments  around  a  central  axis.  In 
all  of  them,  the  body  wall  of  each  individual  animal  is 
made  up  of  two  membranes,  an  outer  and  an  inner ;  all 
are  aquatic,  and,  with  about  four  exceptions,  marine. 
They  all  have  a  central  stomach,  a  mouth  at  one  pole, 
surrounded  by  tentacles  which  are  armed  with  thread- 
cells,  these  latter  being  almost  universal  in  the  sub- 
kingdom.  When  a  nervous  system  exists  it  is  as  an 
obscure  ring,  and  is  related  to  the  margin  at  the  base 
of  the  tentacles. 

The  two  great  classes  of  Coelenterates,  Hydrozoa 
and  Actinozoa  may  be  contrasted  thus  :  the  former 
have.but  one  internal  cavity ;  the  latter  have  a  central 
stomach  cavity  surrounded  by  a  separate,  though 
communicating  body  cavity,  and  the  egg-producing 
organs  open  into  this  second  space. 

The  two  great  sub-classes  of  Actinozoa  are — 

A,  Those  with  simple  tentacles  in  multiples  of  5 
or  6  :  Sub-class  i,  Zoantharia. 

B.  Those  with  pinnate  tentacles  in  multiples  of  4: 
Sub-class  2,  Alcyonaria. 


CHAFFER  IX. 

SUB-KINGDOM   4.      ECHINODERMATA  I   ENCRINITES 
AND   STAR-FISHES. 

General  Characters. — Sea-urchins,  star-fishes,  and  sea- 
cucumbers  make  up  a  natural  assemblage  of  animals, 
called  Echinodermata  on  account  of  the  spiny  skins 


48  Invertebrata. 

found  in  most  species.  They  display  a  radiating  sym- 
metry, but  either  in  the  larval  or  in  the  adult  condition 
there  are  traces  of  a  bilateral  disposition  of  parts.  A 
body  cavity  is  always  present,  containing  within  it  the 
digestive  organs,  and  the  stomach  cavity  never  com- 
municates with  this  surrounding  space  in  the  perfect 
or  adult  animal,  as  it  does  in  the  Coelenterates.  The 
Echinoderms  possess  a  nervous  system  of  radiating 

FIG.  27. 


Section  of  the  purple  Sea  Urchin  (Strongylocentrotits  Ihndus) :  a,  anus ; 
«%  oesophagus  ;  f.  intestine  ;  s,  one  of  the  rods  of  the  tooth  apparatus ; 
nt.  muscles  of  the  jaws  ,  fl,  vessels  of  the  sucking  feet.;  po,  extremity  of 
tne  water  vessel ;  c  a,  ocular  plate  ;  v,  ovary. 

threads;  united  by  a  ring  of  nerve-matter  around  the 
mouth,  and  some  of  them  exhibit  pigment  masses, 
which  are  supposed  to  be  simple  eyes  containing  the 
ends  of  nerve  fibrils  embedded  in  them.  Calcareous 
matter  is  deposited  in  the  skin,  either  in  the  form  of 
spicules,  or  of  plates  which,  by  being  jointed  together, 
build  up  a  shell  or  outer  '  test '  for  the  body. 

When  one  of  our  common  Echinoderms  is  put  into 
a  vessel  of  sea-water,  locomotion  can  be  seen  to  take 


Feather  Stars  and  Stone  Lilies.  49 

place  by  means  of  numerous  little  tubular  processes 
which  project  through  holes  in  the  surface  of  the  shell 
each  of  them  ending  in  a  little  sucking  disk.  There  are 
five  pairs  of  rows  of  these  feet  in  most  species,  and 
these,  by  attaching  themselves  and  then  contracting, 
draw  the  body  of  the  animal  along.  Each  of  these 
pedicelli,  or  little  feet,  as  they  are  called,  is  hollow,  and 
contains  sea  water,  and  there  are  five  long  tubes  in 
each  Echinoderm,  which  pass  meridionally,  and  by  fine 
vessels  convey  the  fluid  into  the  pedicelli  from  a 
tubular  ring  which  surrounds  the  mouth.  To  the 
tubular  system  which  supplies  the  little  feet,  the  name 
Ambulacral  system  is  given.  This  arrangement  of 
water-vessels  connected  with  locomotion  is  peculiar 
to  echinoderms.  The  sub-kingdom  consists  of  four 
chief  classes. 

CLASS  I.  Encrinites  (Crinoidea). — These  animals 
abounded  in  former  times  in  the  seas  of  our  globe,  but 
they  are  now  for  the  most  part  extinct.  The  name  is 
derived  from  the  resemblance  of  many  of  the  fossil 
forms  to  the  flower  of  a  lily,  the  infolded  arms  having 
a  petal-like  appearance.  With  a  few  exceptions,  they 
are  not,  in  their  adult  state,  free  and  capable  of  loco- 
motion, as  are  all  other  Echinoderms,  but  are  fixed 
on  a  jointed  calcareous  stalk.  Though  when  first 
hatched  from  the  egg  all  Crinoids  are  free-swimming 
ciliated  bodies,  yet  very  soon  they  settle  down,  develop 
a  stalk,  and  become  rooted  (fig.  28).  There  is  a  cen- 
tral mouth,  surrounded  by  a  circle  of  movable  arms, 
which  are  often  branched,  and  between  these  arms 
are  little  plates  pierced  by  holes  through  which  the 
ducts  from  the  egg-producing  organs  open.  In  general 


Invertebrata. 


appearance  these  Crinoids  look  like  star-fishes  fixed  on 
central  jointed  stalks,  and  they  are  furnished  with 
feathery  ambulacral  feet  on  their  upper  surface,  which 
as  they  cannot  serve  for  locomotion  seem  to  act  as  gills 
for  breathing.  The  commonest  of  the  living  Crinoids 


FIG.  28. 


FIG.  29. 


Embryo  of  the  Feather  Sta-, 
showing  its  stalked,  encri- 
nite-like  stage. 


Rosy  Feather  Star  (Antedon 
rosacetis),  adult  or  free  con- 
dition. 


becomes  free  in  its  adult  stage,  and  has  a  singular  his- 
tory. Beginning  its  life  as  a  free-swimming  embryo, 
it  soon  becomes  fixed,  and  appears  as  a  stalked  orga- 
nism (fig.  28),  but,  after  existing  in  this  state  for  a 
short  period  it  loses  its  attachment,  becomes  free, 
and  forms  the  exquisitely  tinted  rosy  feather  star,  with 
ten  to  forty  arms,  found  in  our  seas. 

CLASS  II.  Starfishes  (Stellerida),  (fig.  3,  p.  7).— 
T  he  form  of  the  animals  of  this  class  is  expressed  by 


Starfishes. 


FIG.  30. 


the  name.  They  all  possess  a  central  disc  from  which 
five  to  twenty  arms  radiate.  The  surface  is  generally 
roughened  with  stiff  ridges  and  spiny  points,  and 
under  this  layer  is  a  layer  of  calcareous  plates  ;  each 
arm  has  on  its  under  surface  a  groove  in  which  lie 
the  ambulacral  vessels,  and  the  nerve-cord  ;  and  many 
starfishes  have  imperfect  red  eyes  at  the  end  of  this 
ambulacral  groove. 

On  our  sea-shores  there  are  two  kinds  of  star- 
fishes to  be  found,  the  first  kind  or  Brittle-stars  have 
a  rounded,  or  five-sided  flat  disk  at  the  centre,  and 
slender,  jointed,  snake-like  arms,  which,  as  they  do 
not  contain  processes  of  the  viscera,  the  animal  can 
break  off  when  irrita- 
ted. These  brittle-stars 
chiefly  are  found  on  sea- 
weeds. The  other  and 
commoner  kinds  of  star- 
fishes have  thick,  flat- 
tened triangular  arms 
which  are  continuous 
with,  and  not  jointed  to, 
the  disk.  These  have 
a  mouth  in  the  middle 
of  the  under  surface  of 
the  body,  and  around 
it  on  the  skin  are  curi- 

'-IIIQ    little  sninpQ    whnsf 

ous  nuie  spines  wnose 

extremities  are  movable, 

and     two-      or    three- 

bladed,  like  little  pincers.     To  these  little  grasping  or- 

gans,  which   assist  in   seizing    the  prey,   the   name 

£2 


larva  or  Plutens  of  the  Brittle-star 

(pphioiepis). 

mouth;   s,   stomach;   s,    calcareous 
skeleton. 


52  Invertebrate. 

pedicellaria  ('  little  feet ')  is  given.  From  the  central 
stomach,  which  communicates  directly  with  the  mouth, 
long  blind  pouches  extend  into  the  arms  (usually  two 
pouches  into  each  arm)  thus  increasing  the  size  of  the 
digestive  sac.  There  is  an  ambulacral  ring  around 
the  mouth,  and  radial  vessels  extend  from  it  into  the 
arms  to  supply  the  little  feet ;  and  to  convey  sea  water 
into  the  central  ring  there  is  a  canal,  usually  filled 
with  sand,  which  starts  on  the  dorsal  surface  of  the 
disk  from  a  spot  where  there  is  a  wart-like,  finely 
perforated  plate,  which  from  its  likeness  to  a  piece  of 
coral  is  called  the  madreporiform  plate.  Through  it, 
as  through  a  sieve,  the  sea-water  filters  into  the  sand- 
canal,  and  thence  into  the  ring  around  the  mouth. 

Besides  the  ambulacral  vessels,  there  exist  in  star- 
fishes fine  vessels  on  the  surface  of  the  digestive 
cavity,  which  unite  to  form  a  second  vascular  ring 
around  the  mouth ;  this  second  system  is  one  of  blood- 
vessels directly  concerned  in  the  nutrition  of  the  body. 
The  larvae  of  starfishes,  on  leaving  the  egg,  appear 
very  dissimilar  from  the  adults,  looking  like  little 
easels,  and  are  hence  called  plutei  (fig.  30) ;  those  of  the 
brittle-stars  have  a  delicate  calcareous  skeleton,  which 
is  wanting  in  those  of  the  common  five-fingered 
starfishes,  which  in  many  respects  seem  to  resemble 
the  comb-bearing  Hydrozoa.  In  their  adult  states  these 
starfishes  move  mouth-downwards  and  are  extremely 
voracious,  attacking  molluscs,  dead  fishes,  and  other 
kinds  of  animal  matter  in  the  sea. 


Sea  Urchins.  53 


CHAPTER  X. 

SEA  URCHINS  AND   SEA  CUCUMBERS. 

CLASS  III.  Sea  Urchins  (Echinoidea). — The  globular 
or  heart-shaped  sea-eggs,  found  along  our  sea  coasts, 
are  representatives  of  the  next  gioup  of  Echinoderms.. 
In  these  the  surface  is  covered  with  movably  jointed 
spines,  each  of  which  shows  on  section  a  beautifully 
reticulated  structure  which  varies  in  each  species  and 
the  attached  end  of  each  spine  is  hollowed  to  fit  on  a 
tubercle  (fig.  27,  p.  48)  on  the  hard  shell  beneath,  with 
which  it  thus  forms  a  ball-and-socket  joint  On 
removing  the  spines  there  is 
found  under  them  a  shell  com-  FlG-  si- 

posed  of  numerous  flat  angular 
plates,  arranged  in  meridional 
rows.  This  shell  has  the  mouth 
at  one  pole,  which  in  the  living 
animal  is  undermost  and  the  ex- 
cretory orifice  at  the  opposite 

extremity  ;     and    from    mOUth    tO  The  apical  end  of  the  shell 

'.       -..,-.  of  Echinus  esculentus. 

apex  the  Shell  IS  divided  intO  ten       e  anal  opening,     c  ocular 
•  j  •          •.  ,.  f     ,  •    ,        plates,     d  ovarian    plates, 

meridional  Segments,  five  Of  Which      £  maclreporiform  plate. 

consist    of   plates  pierced  with 
holes  for  the  ambulacral  feet,  and  five  of  unperforated 
plates ;  these  are  placed  alternately,  and  each  segment, 
perforated  or  unperforated,  consists  of  two  rows  of 
plates  (fig.  31,  a,  b\ 

The  mouth  is  surrounded  by  a  soft  area  of  skin 
bearing  modified  spines,  modified  tube-feet  and  pedi- 


54 


Invertebrata. 


cellariae,  somewhat  like  those  of  starfishes  ;  the  oppo- 
site or  aboral  pole  is  surrounded  by  five  plates,  each 
placed  at  the  end  of  one  of  the  imperforate  meridians, 
and  each  pierced  by  the  end  of  the  duct  from  one  of 
the  five  large  egg-secreting  glands  which  lie  within 
the  shell  between  the  ambulacra.  Between  these 
ovarian  plates  and  at  the  end  of  the  ambulacra  are 
five  smaller  plates,  each  pierced  by  the  end  of  the 
radial  nerve  threads,  and  bearing  a  little  eye-speck ; 
these  are  called  '  ocular  plates.'  One  of  the  former  set 
of  plates  is  always  unsymmetrical,  swollen,  and  finely 
pierced  with  holes,  being  in  fact  the  combination  of  an 
ovarian  plate  with  the  madreporiform  tubercle  at  the 
end  of  the  sand  canal  as  in  starfishes. 

Sea  Urchins  have  ambulacral  vessels  just  like  those 
of  starfishes,  with  a  tubular  ring  around  the  mouth  and 
FlG.  32.  five    branches,   one 

along  the  inner  sur- 
face of  each  set  of 
perforated  plates, 
through  the  holes  in 
which  the  tube  feet 
project. 

Most  Sea  Urchins 
have  the  mouth 
armed  with  a  com- 
plex system  of  teeth, 
five  of  which  are 
placed  around  the 
orifice  with  their 
points  directed  to- 
wards it,  each  being  situated  in  the  centre  of  a  wedge- 


Tooth  apparatus  of  the  Sea  Urchin,  showing 
the  arrangement  of  the  muscles. 


Sea  Urchins. 


55 


shaped  jaw  (fig.  33),  which  itself  consists  of  two  sym- 
metrical halves.  Twenty-five  accessory  pieces  are  ap- 
pended to  these  parts,  and  the  whole  apparatus  is  moved 
by  thirty  muscles  (fig.  32).  This  apparatus  is  fixed  by 


FIG.  33- 


99 


Jaws  of  the  Sea  Urchin.     A,  two  jaws  seen  laterally  ;  B,  interior  view 
of  a  single  jaw  ;  ft,  surface  of  jaw  ;  /,  teeth. 

muscles  and  fibrous  bands  to  calcareous  loops  which 
project  inwards  at  the  mouth  end  of  the  shell,  and  it 
can  easily  be  dissected  in  the  common  sea  urchin. 
The  larvx  of  sea  urchins  are  pluteus-like,  containing 
a  calcareous  skeleton. 

Two  types  of  sea  urchins  are  found  in  American 
seas.  One  like  the  common  Strongylocentrotus  dro- 
bachiensis  is  globular  or  slightly  flattened,  with  am- 
bulacral  areas  extending  from  pole  to  pole,  and  with 
the  mouth  and  anus  at  opposite  poles  ;  the  other  type, 
represented  by  the  heart-urchin  (Schizaster  fragilis) 
found  in  deep  water,  has  the  anus  not  opposite  to  but 
approximated  to  the  mouth,  and  the  ambulacral  rows 
not  extending  from  pole  to  pole,  but  in  petal-like 
areas  on  one  surface  of  the  shell  alone. 


Invertebrata. 


CLASS  IV.     Sea  Cucumbers  (Holothuroidea).— 

Singular,  elongated  or  cylindroidal  animals,  closely 
allied  to  sea  urchins,  but  without  either  spines  or  hard 
test,  make  up  this  class.  They  are  found  among  the 
tangles  or  in  moderately  deep  water  along  our  shores. 
The  body-wall  is  muscular,  and  contains  in  its  surface- 
layer  calcareous  spicules,  resembling  anchors,  wheels, 
&c.  The  mouth  is  surrounded  by  plumose  ten- 
tacles, and,  on  the  surface  of  the  body  are  rows  of 
tube-feet,  more  irregularly  disposed  than  in  sea 
urchins.  The  intestine  is  often  of  great  length,  and 
ends  in  a  small  aboral  sac  or  cloaca,  into  which  also 
open  (in  most  species)  two  very  remarkable  tree-like 
organs  which  lie  in  the  body  cavity,  and  which  are 
adjuncts  to  the  water- vascular  system  for  purposes  of 
breathing.  In  organisation 
they  resemble  sea  urchins, 
and  often  reach  very  large 
sizes.  In  tropical  seas  some 
of  these  Holothurians  are 
inhabited  by  little  parasitic 
fishes,  and  even  in  temper- 
ate regions  small  shelled 
mollusks  are  found  in  or 
on  their  bodies  as  parasites. 
One  species,  the  Trepang,  is 
imported  in  large  quantities 
from  NE.  Australia  into 
China,  where  it  is  regarded 
as  a  luxury  of  diet. 

Recapitulation. — Echinoderms  are  characterised 
by  the  presence  of  highly  differentiated  tissues,  a  dis- 


FIG.  34. 


Cucumaria  doHolum.     One  of  the 
Sea  Cucumbers. 


Echinoderms,  Worms.  57 

tinct  nervous  system,  a  digestive  canal  which  in  the 
adult  is  separate  from  the  body  cavity  (though  in  the 
embryo,  the  body  cavity  arises  as  an  outgrowth  from 
the  primary  intestine),  a  radiating  symmetry  tending 
to  become  bilateral,  and  a  water-vascular  system 
whose  little  tubular  feet  or  offsets  act  as  locomotory  feet 

The  chief  sub-types  may  be  tabulated  thus — 

A.  Body  stalked  at  some  period  of  life,  ambulacral 
feet  not  locomotory  =  Class  I.  Crinoidea 
(mostly  fossil). 

R  Never  stalked,  star-like,  with  ambulacra  as  organs 
of  locomotion.  =  Class  II.  Stellerida. 

a.  Arms  jointed  to  the  disk,  not  containing 

viscera   =   Order    I.     Ophiuroidea 
(Brittle  Stars). 

b.  Arms  not  jointed,  containing  viscera  = 

Order  II.  Asteroidea  (common  Star- 
fishes). 

C.  Never  stalked,  globular,  disk-like  or  heart-shaped, 

with  a  continuous  test  =  Class  III.  Echinoidea. 

D.  Never  stalked,  elongated,  with  a  soft  integument 

containing  spicules  =  Class  IV.  Holothuroidea. 
The  Echinodermata  are  all  marine,  and  are  never 
united  together  into  colonies. 


CHAPTER  XL 

SUB-KINGDOM   V.  :   VERMES. 

WORMS,    though   often   mean  and   uninteresting  in 
external  appearance,  are  yet  in  many  respects  among 


{    5  8  Invertebrate. 

the  most  curious  forms  in  the  animal  kingdom.  They 
are  elongated,  soft-bodied  creatures,  which  have  their 
organs  arranged  in  a  bilaterally  symmetrical  manner. 
In  many  of  them  the  body  consists  of  successive  seg- 
ments, arranged  in  a  chain,  each  intermediate  segment 
being  like  its  preceding  and  succeeding  neighbours. 
There  is  a  nervous  system  in  most  forms,  consisting 
of  two  or  more  nerve  knots  above  the  pharynx  and  a 
cord  prolonged  backwards  along  the  under  side  of 
the  body,  beneath  the  digestive  canal.  A  water- 
vascular  system  exists  in  some  form  or  other  in  all 
worms,  but  it  has  never  any  connexion  with  the 
function  of  locomotion.  It  usually  consists  of  a  sys- 
tem of  tubes,  one  in  each  of  the  successive  segments 
of  the  body,  opening  by  one  extremity  on  the  surface 
and  by  its  other  end  communicating  with  the  body 
cavity.  These  sets  of  tubes  are  commonly  known 
among  the  higher  worms  by  the  name  of  segmental 
organs.  Blood-vessels  often  exist,  and  sometimes  con- 
tain coloured  blood,  but  there  is  no  heart,  and  the 
colour  does  not  depend  on  the  existence  of  minute 
floating  coloured  corpuscles  in  a  colourless  fluid,  as 
is  the  case  "with  the  blood  of  vertebrates.  The  com- 
mon earth-worm  and  leech  may  be  taken  as  well- 
marked  examples  of  the  sub-kingdom. 

Many  worms  are  parasitic  and  live  within  the 
bodies  of  higher  animals ;  among  these  the  circulatory, 
water-vascular,  and  digestive  systems  become  rudi- 
mental,  the  nervous  system  remains  undeveloped,  the 
body  cavity  often  vanishes,  and  the  reproductive 
organs  alone  are  fully  represented.  This  sub-kingdom 
includes  the  following  classes  : 


Planarians. 


59 


FIG.  35. 


CLASS  I.  Tnrbellaria. — The  simplest  worms 
with  which  we  are  acquainted  are  found  on  the  sea- 
shore, under  or  adhe- 
rent to  stones,  or  else 
in  fresh  water  pools, 
as  small  ciliated,  flat- 
tened soft  bodies, 
which  glide  with  a 
slug-like  motion  over 
wet  surfaces,  or  swim 
by  the  vibrations  of 
their  cilia.  These 
Turbellarians  (so  cal- 
led from  the  commo- 
tion produced  by  their 
cilia  in  the  water 
around  them)  have  a 
mouth  placed  gene- 
rally beneath,  not  at 
the  anterior  extremity, 
and  the  part  of  the 
digestive  canal  imme- 
diately within  the 
mouth  is  protrusible 
as  a  kind  of  proboscis. 
This  contains,  in  some 
of  the  larger  forms,  a  ?'&**** 
spine  or  dart,  which 

is  used  as  a  weapon  of  offence,  and  being  supplied 
with  poison  from  a  little  poison-gland  at  its  base,  acts 
as  a  formidable  weapon  against  the  minute  creatures 
upon  which  these  animals  feed.  The  digestive  canal 


common  Turbelia- 


60  Invertebrata. 

in  the  smaller  flatter  forms  is  often  tree-like,  branched 
(fig.  35).  In  others  it  is  a  simple  pouch  with  no 
excretory  orifice,  but  in  the  larger  forms  it  is  elon- 
gated. The  water-vessels  appear  as  two  lateral  tubes, 
and  the  egg-producing  organs  are  usually  complex. 
The  young  Turbellarians  on  leaving  the  egg  are  usually 
unlike  the  parent,  often  helmet-shaped,  with  a  whip- 
lash-like process  at  the  apex,  but  this  larva  develops 
into  a  worm-like  body  by  moulting  or  shedding  its 
surface.  The  smaller  forms  are  generally  flattened, 
somewhat  elliptical ;  the  largest  are  worm-like,  some- 
times very  long,  and  are  called  Nemertean  worms. 
One  of  these,  Borlasia,  found  not  very  uncommonly 
on  our  own  shores,  has  been  taken  measuring  twelve 
feet  in  length. 

The  2nd,  3rd,  and  4th  classes  of  worms  are  mostly 
parasitic  in  their  habit  and  are  called  suctorial,  round, 
and  thorn-headed  worms  respectively. 

CLASS  II.  Cotylidea. — The  sucker-bearing  worms 
are  so  called  because  they  are  armed  with  rounded  or 
irregular  cup-like  suckers.  These  worms  are  generally 
simple  in  organisation ;  and  their  body  cavities  and 
digestive  organs  are  either  abortive  or  rudimentary. 
The  two  types  of  these  worms  are  Tapeworms  and 
Flukes. 

The  tapeworms  are  so  called  from  their  great 
length  and  flatness.  They  exist  principally  in  the 
digestive  canals  of  higher  animals,  especially  in  fishes. 
The  human  race  is  not  exempt  from  occasionally 
harbouring  at  least  three  species  of  these  parasites. 
One  of  these,  the  common  tapeworm,  or  Tania  solium, 
is  common  in  Britain  and  Western  Europe,  and  may 


Tapeworms. 


61 


FIG.  36. 


be  taken  as  the  type  of  the  order.     On  examination, 

it  presents  to  us  a  very  small  roundish  head  armed 

with  twenty-six  little  hooks  arranged  in  two  rows,  and 

four  round  suckers,  followed  by  a  long  slender  neck, 

at  first  undivided 

but  soon  exhibit-         a        A 

ing     traces      of 

transverse      seg- 

mentation,which, 

as  we  trace   the 

worm   from    the 

head,       become 

more  and   more 

clearly      marked 

until  we  reach  a 

part  Consisting  Of  A,  Proglottis,  or  pei  ect  joint  of  Tapeworm  (Teenia, 
Hictinof  injntc  soliuni)  ;  a,  water-vascular  tube  ;  c,  egg-pro- 

dlStmct          JOintS,        ducing  organ>   B>  Head  of  Ttenia  mediocanel- 

each     of    which      lata' 

joints  contains  a  complete  egg-producing  apparatus. 
When  we  remember  that  these  worms  may  attain 
the  length  of  25  feet,  and  that  there  are  at  least 
twenty  perfect  joints  in  a  foot,  and  that  each  joint 
can  produce  many  scores  if  not  hundreds  of  ova, 
we  can  form  some  idea  of  the  amazing  fecundity  of 
these  parasites.  The  growth  of  the  individual  takes 
place  from  the  head,  so  that  the  oldest  segments  are 
those  which  are  most  remote  from  it  and  the  newest 
are  the  fine  joints  close  thereto. 

The  life  history  of  the  tapeworm  is  curious.  The 
eggs  are  protected  by  a  very  firm  horny  capsule  and 
thus  they  can  maintain  their  vitality  for  long  periods 
of  time,  and  can  resist  maceration  and  even  short 


62     V  Invertebrata. 

exposures  to  high  temperature.  On  entering  the 
digestive  organs  of  some  animal  with  its  food  or  diink, 
the  embryo  is  set  free  and  travels  through  the  tissues 
of  its  new  host  as  a  little  oval  body  armed  in  front 
with  weak  hook-like  or  boring  spines.  On  reaching 
a  suitable  site  it  anchors,  and  the  body  dilates  into  a 
sac  full  of  water.  In  this  cystic  condition  the  animal 
may  remain  stationary  for  a  length  of  time,  and  by 
budding  the  number  of  cysts  is  capable  of  a  rapid 
increase.  When  the  flesh  of  an  animal  containing 
such  cysts  is  eaten  by  another,  the  liberated  saccular 
worm  has  its  outer  wall  dissolved  away,  and  its  inner 
portion  lengthens  and  in  a  short  time  becomes  a  true 
tapeworm.  In  most  cases  it  requires  two  animals  as 
hosts  for  the  proper  perfection  of  the  worm.  Thus 
the  human  tapeworm  has  its  cystic  stage  in  the  flesh 
of  the  pig,  the  condition  of  pork  called  '  measly '  being 
due  to  these  little  cysts  in  the  muscles  of  the  pig. 
Similarly,  the  tapeworm  of  the  dog  develops  from 
cysts  found  in  the  hare ;  that  of  the  cat  from  cystic 
worms  in  the  mouse,  that  of  the  fox  from  cysts  in  the 
field-mouse,  &c. 

In  Ireland,  the  commonest  human  tapeworm  has 
four  suckers  but  no  hooks  on  its  head  (fig.  36  B),  and  is 
known  as  Tcznia  mediocanellata ;  its  larva  inhabits 
the  ox. 

In  Russia  and  Switzerland,  the  human  tapeworm 
is  quite  a  distinct  species,  with  very  flat  body,  no 
hooks,  and  two  long  grooves  on  its  head  in  place  of 
suckers  ;  its  larvae  live  in  the  waters  of  certain  lakes, 
and  it  has  been  supposed  that  it  is  through  these 
waters  being  used  for  drinking  purposes  that  they  gain 
entrance  into  the  human  body. 


Flukes. 


Trematodes    or    Flukes. — The    second    order    of 
sucker-bearing  parasitic  worms  consists  of  the  '  flukes/ 

FIG.  37.  FIG.  38. 


Dittoma  lanceolatum^  the 
liver  fluke,  a,  mouth  ;  b, 
sucker  ;  c,  digestive  canal; 
d.  e,  water-vascular  sys- 
tem ;  A,  kt  reproductive 
organs. 


Oxyuris  vermiciilaris,  the  common  threadworm  of  children. 

met  with  in  the  liver  of  the  sheep,  and  of  allied  forms 
(ng-   37) ;  these  are  not  united  in  chains  as  in  the 


64  Invertebrate 

tapeworms,  but  each  consists  of  a  single  segment  bear- 
ing one  or  two  suckers  (a,  b).  In  many  respects  they 
resemble  the  Turbellarian  worms,  but  are  not  ciliated 
and  often  present  formidable  armatures  of  recurved 
hooks.  They  are  like  tapeworms  in  the  development 
and  complexity  of  their  ovaries,  and  many  of  them 
show  in  their  history  alternations  of  generations  as 
curious  as  those  of  their  relatives  the  tapeworms ;  for 
example,  the  larvae  of  some  liver  flukes  live  for  a  time 
free,  in  water,-  and  develop  within  their  bodies  little 
cylindrical  worms,  which  are  set  free  on  the  bursting 
of  the  wall  of  the  parent,  and  in  turn  enjoy  an  inde- 
pendent life.  Within  these  worms  again  there  may  form 
another  brood  of  internal  buds,  which  also  grow,  burst 
their  envelope,  and  become  for  a  time  free,  but  soon 
attach  themselves  to  some  soft  aquatic  animal  in  whose 
body  they  become  encysted,  to  develop  finally  into  the 
mature  forms  when  their  first  host  is  eaten  by  some 
larger  animal.  Thus  the  flukes  found  in"  water-fowl 
have  their  larvae  in  water  molluscs,  &c.  To  these  flat 
sucker-bearing  parasites  the  name  Trematoda  is  given. 
CLASS  TIL  Nematelmia. — These,  the  commonest 
forms  of  parasitic  worms,  are  cylindrical,  tapering  to 
each  end,  and  possessing  a  body  cavity  (fig.  38.)  They 
are  never  divided  into  successive  joints,  although  their 
surface  may  be  finely  ringed,  and  there  is  always  a 
digestive  canal  with  an  outlet,  as  well  as  a  mouth. 

The  round  worm,  often  found  in  the  small  intes- 
tines of  children,  is  a  good  example  of  the  order.  It  is 
about  seven  or  eight  inches  long,  ringed  on  its  surface, 
with  the  mouth  at  its  anterior  end,  surrounded  by  three 
little  lobes  j  from  this,  a  tube,  the  oesophagus,  passes 


Thread-worms.  65 

to  the  stomacl ,  which  is  a  small  suctorial  muscular 
cavity,  communicating  by  a  straight  intestine  with 
an  outlet  which  is  not  terminal.  Beside  the  common 
round  A  scar  is  lumbricoides,  the  human  digestive  canal 
is  the  occasional  dwelling-place  of  two  other  worms, 
one  of  which,  Oxyuris  vermicularis,  is  a  small  thread- 
like worm  (fig.  38),  the  other  Trichocephalus  dispar^ 
much  more  common,  has  a  very  slender  neck  and  a 
thicker  body.  A  species  closely  allied  to  the  last 
named  is  the  Trichina  spiralis,  a  minute  worm  found 
in  the  flesh  of  pigs,  calves,  &c.,  which  when  introduced 
into  the  human  body,  often  multiplies  rapidly  in  the 
voluntary  muscles  of  the  system,  causing  dangerous 
and  even  fatal  symptoms. 

These  worms  are  as  prolific  as  their  fellow  parasites, 
and  the  early  stages  of  many  live  for  a  time  in  water, 
from  whence  they  enter  into  the  bodies  of  their  hosts, 
and  in  those  whose  life-history  we  know,  the  free  and 
parasitic  conditions  appear  very  dissimilar.  It  has  been 
supposed  and  with  reason  that  most  of  the  free  Ne- 
matelmians  found  in  stagnant  pools  are  early  stages 
of  parasitic  species. 

Gordiacca.  —  The  horsehair-like  thread  -  worm 
which  is  found  in  rainwater  pools  is  an  example  of 
a  second  order  01"  round  worms.  This  remarkable 
animal  begins  life  as  a  little  larva  living  in  mud  or  in 
water  pools  ;  it  is  armed  with  boring  spines,  whereby 
it  pierces  into  the  body  of  a  beetle  or  other  aquatic 
or  terrestrial  insect ;  here  it  becomes  encysted,  and, 
having  grown  in  this  condition  to  a  considerable  length, 
often  ten  times  as  long  as  its  host,  it  becomes  free  and 
aquatic  and  produces  its  eggs.  So  rapidly  do  some 
F 


66  Invertebrata. 

of  these  multiply,  as,  for  example,  the  common  Mermis 
aloicans,  that  they  have  given  rise  to  the  belief  that 
they  have  fallen  as  '  worm-ra.ins.'  These  worms  are 
called  Gordiaceae  and  are  distinguished  from  the  other 
round-worms  by  the  rudimentary  condition  of  their 
digestive  canal.  They  are  also  remarkable  for  their 
extreme  tenacity  of  life,  as  they  can  be  dried  into  hard 
brittle  threads  and  yet  appear  lively  and  active  on 
being  moistened. 

CLASS  IV.  Acanthocephala. — The  '  thorn-headed ' 
worms  are  rounded,  or  cylindrical,  each  with  a  pro- 
trusible  proboscis  armed  with  many  recurved  hooks. 
They  are  remarkable  for  the  total  absence  of  the  mouth 
and  intestine  in  their  adult  condition.  The  common- 
est species  are  found  in  the  intestines  of  swine,  &c., 
with  their  heads  buried  in  the  substance  of  the  wall 
of  the  digestive  tube. 


CHAPTER  XII. 

NON-PARASITIC  WORMS. 

CLASS  V.  Wheel- Animals,  Rotatoria. — On  tracing 
the  development  of  the  more  complex  free  worms  we 
find  that  the  larva,  after  emerging  from  the  egg,  ap- 
pears as  a  free-moving  creature,  with  circlets  of  vibrat- 
ing cilia  aiound  its  extremities,  these  ciliary  lobes 
being  in  some  forms  large  and  rounded  (fig.  47,  A). 

In  rain  pools  and  ditches,  small  creatures  are  fre- 
quently met  with  which  resemble  the  larvae  of  worms, 


Spoon-worms  and  Leeches. 


FIG.  39. 


but  which  remain  permanently  in  this  ciliated  condi- 

tion.    In  these,  the  ciliary  lobes  are  prominent  and 

rounded,  acting  as  locomotory  organs,  and  from  the 

rapid  vibration  of  the  cilia  which  clothe  them  they 

seem   like   rotating  wheels,  hence  these 

little  creatures  are  called  Rotatoria.    They 

are  microscopic  in  size  varying  from  3-^otn 

to  Jth  of  an  inch  in  length,  but  from  the 

exquisite  transparency  of  their  bodies  the 

details  of  their  organisation  can  be  seen 

by  the  aid  of  the  microscope.     The  male 

rotifers  are  few  and  small  and  have  no 

digestive  canal  ;  the  females  have  a  com- 

plex nutritive  system,  and  many  species 

are  provided  with  an  organ  of  mastication 

like  an  anvil  acted  on  by  two  hammers. 

These  animals  can  bear  much  ill  usage, 

and  are  capable  of  reviving  again  on  being 

moistened,  after  having  been  almost  com- 

pletely dried  up. 

On  irritation  the  trochal  disks  (fig. 
39,  c]  can  be  retracted  into  the  cavity  of 
the  body,  from  which  they  are  gradually 
protruded  again  on  the  cessation  of  the 
stimulus.  Some  rotifers  are  rooted  ; 
others  possess  a  forceps  posteriorly, 
whereby  they  can  hold  on  to  foreign 
bodies  ;  others  again  are  contained  in 
sheath,  into  which  they 
being  irritated. 

CLASS     VI.      Spoon-  worms     or    Squirt-  worms, 
Gephyrea.  —  These  are  interesting  marine  worms  whose 

F  2 


a  vase-like 
can  retract   themselves,  on 


68 


Invertebrate 


elongated  or  sac-like  bodies  contain  a  long  tortuous  in- 
testine, ciliated  inside  and  outside.  They  rarely  exhibit 
a  division  into  segments,  nor  have  they  locomotory  pro- 
cesses of  any  kind,  and  they  never  have  any  calcareous 


FIG.  40. 


FIG.  41. 


Tooth  and  Muscles 
of  Leech. 


Embryo  Leech.    Adult  Leech. 
Mouth  of  Leech. 

or  siliceous  spicules  in  their  skin,  although  sometimes 
there  are  a  few  bristles  scattered  on  the  surface.  The 
mouth  is  at  the  anterior  end,  and  it  is  provided  with 
a  protrusible  proboscis,  sometimes  of  great  length. 

CLASS  VII.  Leeches. — The  next  group  of  worms 
is  exemplified  by  the  common  horse-leech  or  by  the 
medicinal  leech.  They  are  soft-bodied  annulated 
worms  which  live  parasitically  on  the  outside  of  verte- 
brated  animals,  from  which  they  draw  their  nourish- 
ment. Their  bodies  are  composed  of  segments,  which 
are  indistinctly  or  not  at  all  marked  from  each  other 


Leeches. 


69 


on  the  surface,  but  can  easily  be  distinguished  within, 
as  the  organs  of  the  body  are  arranged  in  successive 
groups.  Leeches  have 
at  their  front  end  a 
sucker,  and  some  have 
a  second  suctorial 
disk  at  the  hinder  ex- 
tremity, and  several 
species  are  even  pro- 
vided with  lateral 
suckers.  The  mouth 
is  generally  situated  in 
the  front  sucker,  and 
it  is  armed  with  three 
horny  jaws  or  plates 
(fig.  41)  with  serrated 
edges.  These  plates 

act  as  teeth,  enabling  the  leech  to  make  incisions  in  the 
skin  of  its  host  through  which  to  suck  the  blood. 
The  digestive  canal  is  straight  and  consists  of  a  central 
tube  with  a  row  of  blind  pouches  along  each  side 
(fig.  42,  B)  which  can  become  distended,  hence  the 
body  can  take  in  a  great  quantity  of  blood. 

There  is  a  nerve-ganglion  in  each  segment  of  the 
body,  the  first  (fig.  42,  c)  of  these  is  comparatively 
large  and  made  up  of  several  smaller  ganglia  grouped 
together;  the  successive  ganglia  are  united  into  a  chain 
by  fine  filaments  and  they  lie  on  the  ventral  or  under 
side  of  the  digestive  organs. 

Leeches  possess  proper  blood-vessels  in  which 
their  own  nutritive  fluid  circulates.  Their  water- 
vascular  system  takes  the  form  of  a  series  of  segmented 


A  Reproductive  organs  of  leech.  B  Di- 
gestive canal  of  leech,  c  Nervous  sys- 
tem of  Malacobdella. 


70  Invertebrata. 

organs  or  tubes  opening  laterally,  one  on  each  seg- 
ment. The  egg-producing  organs  are  very  complex. 

Locomotion  takes  place  by  the  suckers  :  the 
hinder  one  being  fixed,  the  animal  elongates  itself 
and,  fixing  its  front  sucker,  sets  free  the  hinder  one, 
then  shortening  its  body  it  proceeds  in  a  similar  manner. 
Leeches  can  also  swim,  and  when  so  progressing  the 
body  becomes  flattened  by  the  contraction  of  vertical 
muscular  fibres  which  run  from  the  dorsal  to  the  ven- 
tral surface,  and  then  by  undulating  movements  it 
advances  like  a  wavy  ribbon. 

Medicinal  leeches  are  principally  imported  from 
Hungary  and  Sardinia. 


CHAPTER   XIII. 

NON-PARASITIC   WORMS. 

CLASS  VIII.   Bristle-footed  Worms  (Chsetopoda).— 
•We  can  scarcely  turn  over  a  stone  on  the  sea  shore 

FIG.  43. 


Transverse  section  of  a  Worm,  of  Amphioxus,  and  of  a  Vertebrate  contrasted. 
a,  outer  or  skin  layer  ;  b,  dermal  connective  layer  ;  c,  muscle  plates  ; 
d,  segmental  organ  ;  h,  arterial,  and  i,  venous  blood-vessel ;  g,  intes- 
tine ;  /,  notochord. 

without  finding  under  it  some  species  of  the  group  of 


Worms. 


bristle-bearing  worms,  a  class  of  which  the  lug-bait  or 
the  hairy- bait  of  fishermen  may  be  taken  as  represen- 
tatives. These  worms  have  bodies 
made  up  of  a  succession  of  simi- 
lar joints,  and  their  locomotion, 
either  creeping  or  swimming,  is 
accomplished  by  means  of  little 
stumpy  bristle-bearing  eminences, 
with  which  their  bodies  are  pro- 
vided. Each  joint  of  the  body 
exhibits  two  pairs  of  these  pro- 
cesses, two  of  which  are  on  the 
upper  or  dorsal  surface,  and  two 
are  on  the  ventral  or  under  sur- 
face, oae  on  each  side  of  each 
surface  ;  these  are  known  as  dorsal 
and  ventral  oars.  The  mouth  is 
on  the  second  segment,  and  is 
often  armed  with  sharp  teeth. 
The  intestine  is  usually  straight 
and  very  often  has  lateral  pouches 
appended  to  it  like  those  in  the 
leeches.  There  is  a  vascular 
system  consisting  of  long  tubes, 
dorsal,  ventral  and  lateral,  and  the 
blood  contained  in  these  is  often 
red,  green,  or  white.  The  gills 
are  usually  arranged  along  the 
dorsal  surface  of  the  body  spring- 
ing close  to  the  root  of  the  dorsal 
oar,  and  in  these  the  blood  is  purified  by  being  exposed 
to  the  oxygen  held  in  solution  in  the  sea-water. 


Arenicola  piscatorutit 
Lug-bait  worm. 


72  Invcrtebrata. 

There  are  also  segmental  tubes  opening  one  on  each 
side  of  each  segment,  and  sometimes  the  eggs,  which 
are  produced  within  the  body,  escape  through  these 
canals.  The  chain  of  nervous  ganglia  is  also  well- 
developed.  Some  worms  secrete  a  glutinous  material 
from  their  surface,  which  cements  together  sand-grains 
and  other  foreign  bodies  into  a  tube  wherein  the  animal 
lives.  Other  worms  secrete  from  their  surface  cal- 
careous matter  which  makes  up  a  tube  as  a  dwelling- 
house,  in  which  the  animal  is  permanently  contained. 
Such  forms  have  the  gills  developed  only  on  the  fore- 
most segments  of  the  body,  and  have  the  dorsal  and 
ventral  oars  of  all  the  other  joints  rudimentary ;  but 
they  possess  tentacle-like,  branching  processes  about 
the  head.  Of  these  the  common  Serpula,  whose  white 
calcareous  snake-like  concretions  are  so  common  on 
the  stones  and  shells  on  the  sea  shore,  and  the 
Spirorbis,  whose  minute  white  whorled  shells  dot  the 
surface  of  the  shore-tangles,  are  examples. 

A  few  worms  are  phosphorescent ;  many  others, 
ike  the  sea-mouse,  are  clad  with  iridescent  scales  and 
bristles. 

The  common  earthworm  has  much  smaller  and 
fewer  bristles,  which  are  in  the  form  of  recurved 
hooks,  not  elevated  on  stumpy  processes  of  the  sur- 
face. The  body  is  closely  ringed  and  tapers  from  the 
middle  forwards  to  an  acute  point  in  front.  Each 
ring  bears  its  armature  of  hooks,  which  can  easily  be 
felt  by  drawing  the  body  of  a  worm  between  the 
fingers  from  tail  to  head,  although  they  are  scarcely 
to  be  detected  when  we  feel  the  body  in  the  reverse 
direction.  In  beginning  to  burrow,  the  worm  lengthens 


Worms.  73 

its  body  and  pushes  its  sharply  pointed  head  into  the 
mass  of  soil  which  it  is  about  to  perforate,  then  having 
insinuated  the  few  foremost  rings  of  its  body  into  the 
mould,  the  whole  animal  contracts  in  length,  thus 
swelling  the  front  of  the  body  in  thickness  and  for- 
cibly dilating  the  opening  made  by  its  fore  part, 
the  worm  being  prevented  by  its  hooks  from  slipping 
out  of  the  opening ;  then  it  again  lengthens  its  body 
in  front,  its  hooks  giving  it  a  fixed  point  from  which 
to  act,  and  by  a  succession  of  such  elongations  and 
thickenings  it  can  '  worm '  its  way  through  even  a 
hard  gravel  walk. 

The  mouth  of  an  earthworm  is  placed  on  the 
second  segment,  near  the  apex  of  the  body,  and  from 
it  the  digestive  canal  extends  as  a  straight  tube  through 
the  body.  This  tube  is  very  wide  and  is  always  found 
full  of  earth,  as  these  animals  devour  large  quantities 
of  the  soil  for  the  sake  of  the  organic  particles  con- 
tained in  it,  the  remaining  part  being  passed  out,  and 
heaped  by  the  worms  at  the  outlet  of  their  burrows, 
as  *  wonn  casts.'  For  the  better  division  of  the  mate- 
rial swallowed,  the  digestive  canal  is  provided  with  a 
muscular  gizzard  about  fifteen  rings  behind  its  mouth. 
The  eggs  in  earthworms  are  produced  in  the 
body  cavity  beginning  at  a  point  about  seven  rings 
rom  the  mouth,  and  they  usually  fill  the  body  for 
ibout  seven  segments,  distending  it  and  producing  a 
thick  white  band  or  ring  which  we  often  notice  in  the 
body  of  worms  during  early  autumn.  Worms  are 
propagated  exclusively  by  eggs,  the  common  belief 
that,  when  cut  in  pieces,  each  part  is  capable  of  inde- 
pend'.nt  life  not  being  strictly  true.  If  we  divide  an 


*4  Invertebrata. 

earthworm  about  its  middle,  the  hinder  segment  dies 
after  a  short  time  ;  the  fore  segment  will  probably  live 
and  its  wound  heal.  Similarly,  if  we  cut  the  anterior 
four  or  five  segments  away  the  small  fore  fragment 
will  soon  die,  while  the  large  hind  mass  will  recover. 


CHAPTER  XIV. 

MOSS   POLYPS   AND   TUNICARIES. 

CLASS  IX.  Moss  Polyps  (Bryozoa).— The  broad 
leathery  fronds  of  the  tangles  along  our  shores  are 
often  encrusted  with  beautiful  lace-like  patches  of 
regular  and  minute  patterns.  If  we  put  a  fresh, 
living  piece  of  this  into  a  vessel  of  sea-water,  we 
find  that  each  of  the  cell-like  spots  is  the  home 
of  an  elegant  little  organism  which  may  be  seen  to 
protrude  through  the  mouth  of  its  cell  a  delicate  little 
crown  of  tentacles.  Each  colony  of  these  animals 
consists  of  a  common  stock,  bearing  numerous  little 
cells,  and  each  cell  contains  its  delicately  organised 
inhabitant.  Some  of  the  little  creatures  become 
modified  into  bird's-beak-like  graspers  with  two  horny 
jaws,  for  the  protection  of  the  colony  (fig.  45,  B)  ; 
others  become  altered  into  globular  pouches  for  the 
reception  of  the  eggs  after  their  extrusion.  Each  of 
the  dwellers  in  these  little  cells  consists  of  a  saccular 
body  containing  a  looped  digestive  canal,  in  the  bend 
of  which  a  nerve  ganglion  is  placed,  and  it  is  provided 
with  a  crown  of  hollow  tentacles  guarding  the  mouth. 
Most  of  these  moss-polyps  are  marine  and  have 


Tunicata, 


a  circular  protrusible  basis,  supporting  the  tenta- 
cles ;  some  few  are  inhabitants  of  fresh  water,  and 
these  have  the  tentacles  on  a  horse-shoe-shaped  basis ; 
these  also  have  a  little  valve  to  shut  the  mouth,  which 
is  present  in  only  two  of  the  marine  forms.  Each  of 
the  little  constituent  animals  of  one  of  these  colonies 
has  its  own  digestive  canal,  its  own  nervous  system, 

FIG.  45. 


A.  Natural  size  of  Acamarchis  avicuJaria,  one  of  the  Moss  Polyps  ; 

B.  Magnified  view  of  one  Polype,  showing  its  'bird's  head.' 

and  its  own  egg-producing  apparatus,  and  these  are 
essentially  like  the  corresponding  organs  in  worms. 

CLASS  X.  Tunicata. — These  also  are  marine  soft- 
bodied  animals,  met  with  in  abundance  attached  to 
shells  and  stones  among  the  tangles  on  our  sea  shores. 
They  are  often  called  sea- squirts,  on  account  of  their 
ejecting  little  jets  of  water  from  their  terminal  open- 
ings when  irritated.  They  appear  as  irregular  or  oval 


76 


Invertebrata. 


cated  worm . 
A,  Pharynx,  or  re^pira 
tory 
body  ; 


masses  of  semi-transparent,  often 
gristly  material,  and  of  a  whitish, 
pink,  or  brownish  colour.  They 
vary  in  length  from  i  to  6  inches. 

In  each  tunicary  there  are  two 
apertures  on  the  surface;  one  of  these 
(c,  fig.  46)  opens  into  a  large  chamber 
whose  wall  (e)  is  a  vascular  mem- 
brane, and  at  the  bottom  of  which 
is  the  mouth  (k).  The  digestive  canal 
ends  at  the  bottom  of  a  second 
chamber  (/"),  of  which  the  lower  or 
hinder  opening  is  the  outlet.  Be- 
tween these  two  chambers,  which 
thus  lie  over  the  digestive  canal, 
there  is  a  partition  wall  which  is 
pierced  by  many  small  holes  whereby 
the  water  which  enters  into  one  can 
pass  into  the  other,  thus  bathing  the 
surface  of  the  lining  membrane,  and 
enabling  the  blood  contained  in  the 
spaces  in  its  texture  to  become 
aerated.  The  first  chamber  (fig.  46) 
is  called  the  branchial  chamber,  the 
second  is  called  the  atrial. 

Between    the    opening    of    the 
branchial  chamber  and  the  atrial  ori- 
fice there  is  a  nerve  ganglion  send- 
a  tuni-  mg  a  fine  1°°P  of  branches  around 
the  mouth.     The  heart   lies  at  the 


ocy    Bstmac      c 

egg-producing  organ!  it  the  vessels  pass  into  the  wall  of 


Summary.  yj 

the  branchial  chamber.  In  the  action  of  this  heart  a 
curious  appearance  is  observed  ;  the  blood  is  driven 
by  this  vessel  first  from  one  end  to  the  other,  for  a 
second  the  action  stops,  then  it  is  resumed  in  the 
opposite  direction,  again  another  cessation,  and 
another  reversal,  &c. 

The  *  tunic/  or  outer  wall  (/)  contains  a  starch-like 
compound  which  is  interesting  as  it  is  almost  the  only 
instance  of  the  occurrence  of  a  starch-like  compound 
in  the  Animal  Kingdom. 

Young  tunicates  as  they  emerge  from  the  egg 
appear  as  small,  tailed  larvae,  with  bodies  consisting 
of  two  cavities.  The  axis  of  the  tail  consists  of  a 
cartilaginous  or  gristly  rod  :  in  one  cavity  of  the  body 
the  nerve  ganglion  is  developed,  in  the  other  space  the 
viscera  are  formed.  Thus  they  foreshadow  the  struc- 
ture of  vertebrate  animals. 

Tunicaries  are  sometimes  solitary,  but  many  species 
are  found  united  into  social  assemblages,  and  this 
union  may  go  as  far  as  the  perfect  union  of  the 
blood-vessel  systems,  a  single  vascular  apparatus  sup- 
plying the  whole  colony.  In  one  group,  the  Salpae, 
there  is  an  alternation  of  generations,  solitary  and 
colonial  forms  succeeding  each  other  in  a  cycle. 

Many  of  the  tunicates  are  phosphorescent, 
Pyrosoma,  a  compound  form  inhabiting  the  Atlantic 
ocean,  being  the  most  vividly  luminous  animal  met 
with  in  the  seas. 

Summary. — The  chief  types  of  worms  may  be 
tabulated  thus : 

i.  Unjointed,  ciliated,  non-parasitic  forms  without 
ciliated  head-lobes  =  Class  Turbellaria, 


78  Invertebrata. 

2.  Unjointed  or  obscurely  segmented  minute  forms, 

with  ciliated  head-lobes  =  Class  Rotatoria. 

3.  Parasitic,  flat-bodied  forms,  with  no  body  cavity, 

and  provided  with  suckers  =  Class  Cotylidea. 

4.  Parasitic  forms   with   no   suckers   nor   digestive 

canal,  and  with  a  hook-bearing  proboscis  = 
Class  Acanthocephala. 

5.  Cylindrical,   unjointed,   non- ciliated  forms,   with 

digestive  canal  and  body  cavity,  mostly  para- 
sitic =  Class  Nematelmia. 

6.  Segmented  forms  with  a  proboscis,  and  convoluted 

intestine,  non-parasitic  =  Class  Gephyrea. 

7.  Segmented,  bristle-clad  worms  with  no  suckers. 

moderate     intestine,    non -parasitic    =    Class 
Chaetopoda. 

8.  Segmented,    unbristled,    sucker-armed,    external 

parasites  =  Class  Hirudinea. 

9.  Sessile,  one-jointed,  colony-building  worms  living 

in  cells  and  with  a  crown  of  protrusible  tenta- 
cles =  Class  Bryozoa. 

10.  Sessile  or  free,  one-jointed  worms,  with  one  nerve 
ganglion  but  no  protrusible  crown  of  tentacles 
=  Class  Tunicata. 


CHAPTER  XV. 

SUB-KINGDOM   VI.   MOLLUSCA,    SOFT-BODIED  ANIMALS. 

THIS  division  includes  all  such  forms  as  oysters, 
whelks,  snails,  and  cuttlefishes.  Most  of  these  are 
aquatic  and  in  none  is  there  an  inner  skeleton  (except 
some  small  gristly  organs  in  cuttlefishes)  nor  are  there 


Molluscs. 


79 


any  limbs,  properly  so  called,  in  the  whole  group 
The  outer  tunic  of  the  body  is  generally  thick  and 
extended  to  form  a  leathery  envelope  or  mantle,  the 
outer  surface  of  which  secretes  a  shell  of  carbonate  of 
lime  for  the  protection  of  the  animal. 

The  earliest  condition  of  existence  of  a  mollusc, 
after  it  has  left  the  egg-stage,  is  as  a  small  ciliated, 
worm-like  body  having  at  its  head  an  expanded  lobe, 
richly  clothed  with  cilia  and  resembling  the  trochal 


Larval  forms  of  Worms  and  M  olluscs.  A,  Larva  of  a  Gephyrean  Worm  ; 
B,  c,  Larvae  of  Molluscs,  showing  the  ciliated  velum  v,  and  the  rudi- 
mental  foot,  f. 

discs  of  a  rotifer,  or  the  tentacle-bearing  basis  of  the 
moss-polyps  (fig.  47,  B).  This  process  is  lost  in  the  adult 
in  general,  but  is  interesting  as  one  of  the  many  eviden- 
ces of  the  relationship  between  worms  and  molluscs. 
The  shells  secreted  by  molluscs  consist  of  one, 
two,  or  several  valves,  or  pieces,  and  are  very  various 


So  Invcrtebrata. 

in  shape,  and  often  brightly  coloured.  All  molluscs 
have  a  digestive  canal,  and  sometimes  a  complex 
arrangement  of  teeth.  They  have  like- 
wise a  nervous  system  consisting  of  a 
ring  around  the  fore-end  of  the  diges- 
tive canal,  on  which  are  formed  ganglia 
over  and  under  the  tube ;  besides  this 
there  are  often  other  nerve  masses  and 
organs  of  sense.  There  is  a  heart  which 
propels  the  blood,  but  there  are  few 
or  no  blood-vessels,  the  circulation 

Lamp-shell  or  Te-  .  .  ... 

rebratuia,    one  being  chiefly  carried  on  in  the  inter- 

of  the    Brachio-  -     .  ™.  ,  , 

pods,  dorsal  sur-  spaces  of  the  tissues.  I  here  is  rarely 
much  of  the  body-cavity  to  be  found 
free,  with  the  exception  of  a  small  space  around  the 
heart,  which  is  called  the  pericardium,  and  from  this 
two  short  tubes  pass  out  representing  the  segmental 
organs  of  worms.  Four  classes  are  included  in  this 
sub-kingdom. 

CLASS  I.  Brachiopoda. — Of  this  class  compara- 
tivey  few  representatives  are  now  living,  and  these  in 
few  places,  usually  at  considerable  depths  in  the  sea ; 
but  at  an  earlier  period  of  the  world's  history  they 
were  very  abundant.  They  possess  shells  of  two 
valves,  one  of  which  is  large,  placed  ventrally  or  down- 
wards, and  having  a  beak  pierced  with  a  hole,  through 
which  a  foot-stalk  projects  whereby  the  animal  is 
anchored.  The  other  valve  is  smaller  and  placed  dor- 
sally  ;  it  bears  on  its  inner  surface  a  delicate  shelly  loop 
for  the  attachment  of  the  peculiar  arms  from  which 
the  name  of  the  class  is  derived.  The  valves  are 
joined,  either  by  horny  matter  as  in  the  duck-bill 


Shells  of  Bivalves.  8 1 

shells  (Lingula)  of  Australia,  or  by  tooth-like  hinges, 
as  in  the  lamp-shells  (Terebratu/a),  and  there  are 
several  muscles  for  opening  and  others  for  closing 
the  valves.  The  mantle  in  Brachiopoda  is  full  of 
blood-spaces,  which  are  the  only  breathing  organs  in 
these  animals,  and  there  is  said  to  be  a  heart  lying  on 
the  stomach  for  driving  on  the  blood.  Some  anato- 
mists dispute  the  presence  of  a  heart,  and  claim  that 
the  blood  is  impelled  through  the  body  by  ciliary  ac- 
tion alone. 

The  larvae  of  Brachiopoda  are  freely  locomotive 
and  possess  eyes  and  ear-sacs,  but  the  eyes  disappear 
in  the  fixed  adult  in  which  the  ciliated  head  lobe  of 
the  embryo  becomes  converted  into  the  basis  of  the 
arms.  These  arms  are  long  and  hollow,  usually  spiral 
and  clothed  with  tentacles,  and  their  to-and-fro  mo- 
tions cause  currents  which  bring  the  food  within  the 
reach  of  the  mouth  of  the  stationary  animals. 

CLASS  II.  Lamellibranchiata. — More  familiar  to 
us  are  the  representatives  of  the  second  great  group 
of  molluscs,  oysters,  mussels,  cockles,  &c.  These 
are  easily  recognised  by  their  bivalve  shells,  and  by 
the  two-lobed  mantle  under  whose  folds  are  the  gills 
or  breathing  organs  arranged  in  layers  or  lamellae. 

The  freshwater  mussel,  or  the  large  Mya  or  clam, 
easily  found  along  our  coasts  buried  in  the  sand,  out 
of  which  the  tips  of  their  long  siphonal  tubes  project, 
are  good  examples.  The  shell  of  one  of  these  ex- 
hibits to  us  a  beak  or  point  on  each  valve,  and  is 
marked  by  numerous  lines  parallel  to  its  margin ;  the 
inner  surface  also  differs  in  texture  from  the  outer, 
being  whiter  and  often  exhibiting  a  mother-of-pearl 


82  Invertebrata. 

lustre.  The  cause  of  the  difference  in  appearance  is 
seen  on  making  a  microscopic  section  through  a  shell, 
as  the  outer  surface  is  composed  of  long,  nearly  ver- 
tical, prisms,  while  the  inner  surface  consists  of  fine 
layers  whose  edges  overlap  each  other.  These  edges 


Diagram  of  the  anatomy  of  a  Lamellibranch,  or  Bivalve  Mollusc,  g,  stomach ; 
i  intestine  surrounded  by  the  liver,  the  two  tubes  on  the  left  marked 
by  arrows  are  the  canals  of  the  siphon,  a,  the  anus  ;  b,  hinder  adductor 
muscle  ;  c,  heart ;  d,  nerve  ganglia  ;  e,  fore  adductor  muscle  ft  mouth  ; 
h,  gills. 

are  often  finely  waved,  and  so  decompose  the  rays  of 
light  which  fall  on  them,  thus  producing  the  iridescent 
appearance  seen  in  so  many  shells.  The  nacreous  or 
mother-of-pearl  layers  are  secreted  by  the  surface  of 
the  mantle,  while  the  prismatic  material  is  formed  by 
the  margin  of  that  structure.  Thus  the  shell  is  con- 
stantly increasing  in  size  by  the  formation  of  new 
prismatic  matter,  the  lines  of  growth  being  the  con- 
centric curves  before  noticed.  The  edge  of  the  mantle 


Structure  of  Bivalve  Molluscs. 


FIG. 


is  sometimes  fringed,  and  the  irregularities  secrete 
corresponding  processes  on  the  shell  in  the  forms  of 
ridges,  spines,  £c. 
On  the  inside  of  the 
shell  a  line  of  demar- 
cation shows  where 
the  nacre-secreting 
surface  ends,  and  the 
prism- secreting  por- 
tion begins,  this  is 
called  the  pallial  line 

(fig-  5°)- 

Hinge. — The  two 

Valves      Of    the     Shell  Shell  of  Galathea,  showing  the  hinge,  mantle 

inLamellibranchsare 

usually  similar  to  each  other;  they  are  disposed  late- 
rally, one  on  the  right  and  one  on  the  left,  and  are 
united  by  a  hinge  of  interlocking  teeth  at  the  dorsal 
margin.  A  highly  elastic  ligament  unites  the  valves 
outside  to  the  hinge,  and  is  so  arranged  that  it  keeps 
the  valves  slightly  open.  On  the  inside  of  <a  bivalve 
shell  there  are  to  be  seen  one  or  two  oblong  scars 
in  each  valve  to  which  are  attached  muscles  running 
from  valve  to  valve  for  the  purpose  of  closing  the  shell, 
and  hence  called  adductor  muscles. 

Soft  Parts  of  Bivalves. — The  lobes  of  the  mantle 
are  usually  more  or  less  united  along  the  under  bor- 
der, and  are  often  prolonged  backwards  into  a  long 
tube  or  siphon  which  projects  at  the  hinder  end  of 
the  body;  when  this  tube  exists,  the  pallial  line  is 
indented  posteriorly  into  a  sinuosity  called  the  pallial 


sinus. 


G  2 


84  Invertebrata. 

Many  bivalves  are  fixed  in  the  adult  state ;  in  the 
oyster,  scallop,  &c.,  the  animal  lies  on  one  side,  the 
under  shell  adhering  to  the  surface  on  which  it  rests. 
The  common  mussel  is  fixed  by  means  of  an  anchor- 
age of  strong  fibres  (called  byssus)  secreted  by  a 
gland  on  its  foot.  Under  each  lobe  of  the  mantle 
lie  the  lamellar  gills,  between  which  is  a  fleshy  pro- 
trusion, the  foot  or  organ  of  locomotion.  At  the 
front  is  the  mouth  (fig.  49,  f)  from  which  the  diges- 
tive tube  is  continued  backward,  to  open  above  the 
posterior  adductor  muscle  as  seen  in  the  sketch. 
The  last  portion  of  this  digestive  tube  passes  right 
through  the  cavity  of  the  heart.  The  siphon,  when 
it  exists,  is  a  double  tube,  consisting  of  an  upper 
and  a  lower  passage ;  through  the  latter  the  food  and 
water  for  breathing  purposes  enter  into  the  mantle 
cavity  and  bathe  the  gills ;  through  the  upper  tube 
the  excreted  matter  and  the  water  returning  from  the 
gills  are  ejected.  There  is  a  nerve  ganglion  above 
and  below  the  digestive  canal  at  the  base  of  the  little 
lobes  around  the  mouth  (*  labial  tentacles,'  seen  in 
fig.  49  as  lancet-like  processes),  and  another  exists 
in  the  foot  below  the  digestive  tube ;  a  fourth  is 
placed  posteriorly  beneath  the  hinder  adductor  muscle. 
These  animals  have  no  recognisable  head,  but  some 
of  them  have  eyes  on  the  siphon,  as  in  the  razor- 
shell  (Solen);  others  have  eyes  along  the  edge  of 
the.  mantle  lobes,  as  in  the  common  scallop.  The 
larvae  of  all  bivalves  have  eyes,  but  these  are  lost 
in  the  course  of  development,  and  when  such  organs 
appear  in  the  adult  they  are,  of  secondary  forma- 
tion. 


Gasteropod  Molluscs.  85 

Bivalves  are  wonderfully  prolific ;  the  freshwater 
mussel  has  been  estimated  to  lay  between  two  and 
three  millions  of  eggs  in  a  season,  and  the  oyster, 
it  is  computed,  will  produce  over  half  a  million  of 
eggs  in  a  year. 

Classification. — Bivalves  are  subdivided  accord- 
ing to  the  number  of  the  adductors,  according  to 
the  equality  or  inequality  of  the  two  adductors  when 
both  are  present  and  (when  there  are  two  equal  ad- 
ductors) according  to  the  presence  or  absence  of  a 
pallial  sinus  (page  82).  The  oyster  is  an  example  of 
the  group  which  has  one  adductor.  The  mussel,  of 
the  group  with  two  unequal  adductors.  The  fresh- 
water mussel  and  the  cockle  are  examples  of  the  group 
with  two  equal  adductors  and  no  pallial  sinus,  and 
the  gapers,  stone  borers,  and  razor-shells,  belong  to 
the  section  with  equal  adductors  and  a  pallial  sinus. 


CHAPTER   XVI. 

HEAD-BEARING   MOLLUSCS. 

CLASS  III.  Cephalophora. — The  snail,  whelk  and 
limpet  are  examples  of  a  class  of  molluscs,  each  of 
which  has  a  distinct  head  furnished  with  sensory 
organs,  such  as  eyes,  ear-sacs  and  feelers.  These 
possess  a  mouth  armed  with  teeth,  arranged  on  a  rib- 
bon placed  at  the  bottom  of  the  mouth  cavity ;  this 
band  can  be  drawn  backwards  and  forwards  by  a  set 


86 


Invertebrata. 


of  muscles,  and  thus  can  act  like  a  chain  saw.    This 
band  can   be   easily  found  in    the  common   limpet 

or    whelk,  where     it 


FIG.  51. 


exceeds    an    inch   in 


In  all  but  the 
little  elephant's  tooth 
shell,  the  mantle 
lobes  do  not  entirely 
include  the  body,  and 
the  shell  consists  only 

Tooth    ribbon   or  radula  of  the  Whelk  or 

Buccinum;    a,  c,  lateral  teeth  of  one  row  ;  of      One       Valve.          It 

*'m<  varies  in  shape,  some- 

times being  conical  as  in  the  limpet,  but  usually  it  is 
spirally  coiled,  the  curvature  being  due  to  the  mode 
of  growth,  as  one  side  of  the  animal  grows  rapidly, 
the  other  slowly,  or  not  at  all  ;  hence  the  body  becomes 
coiled  towards  the  aborted  side,  and  the  gills  and 
other  organs  are  generally  developed  only  on  one  side. 
In  most  coiled  shells,  curvature  is  towards  the  left 
side,  throwing  the  mouth  round  to  the  right  side  ;  in 
a  few  rare  cases,  or  as  an  anomaly  of  growth,  the  coil 
may  be  reversed,  winding  to  the  right,  and  with  the 
mouth  at  the  left  side.  The  bodies  of  these  molluscs 
usually  project,  but  they  can  be  retracted  into  their 
shells.  Progression  takes  place  with  a  gliding  motion, 
produced  by  the  undulatory  movement  of  the  under 
side  of  the  foot,  as  may  be  seen  by  placing  a  snail  on 
the  outside  of  a  window  pane,  and  watching  it  from 
within.  The  foot  sometimes  bears  at  its  hinder  part 
a  little  shelly  lid  which,  when  the  animal  is  retracted 
into  the  shell,  acts  as  a  door  to  shut  up  the  cavity  ; 


Sense  Organs  of  Molluscs.  87 

this  lid  (or  opercuhini)  can  be  seen  in  the  whelk  and 
it  is  in  shape  similar  to  the  outline  of  a  section  across 
the  opening  of  the  last  whorl  of  the  shell. 

The  mouths  of  some  shells  are  channeled  at  their 
front  end  (the  end  farthest  from  the  coiled  part),  and 

FIG.  52. 


Diagram  of  the  Anatomy  of  a  Whelk,  the  shell  being  removed,  c,  stomach'; 
e,  end  of  the  intestine ;  g,  gills  ;  d,  auricle  :  h,  ventricle  of  the  heart ; 
J",  nerve-ganglia  of  the  mouth  ;  b,  salivary  gland. 

sometimes  at  their  posterior  end ;  these  channels  are 
for  siphon -like  tubes,  and  as  a  general  rule  such 
molluscs  as  possess  these  siphons  are  carnivorous, 
while  those  with  unchanneled  or  entire  edges  are 
herbivorous. 

Some  univalves,  like  the  common  snail  and  slug, 
live  on  dry  land ;  in  such  forms  gills  would  be  useless, 
and  hence  they  are  absent,  and  a  part  of  the  mantle 
cavity  is  set  apart  for  air-breathing,  and  the  lining  of 
this  region  is  full  of  dilated  blood-vessels.  The 
mouth  of  this  air-chamber  is  small,  and  can  be  seen 


88  Invertebrate*. 

opening  and  closing  periodically  in  the  common 
black  slug  on  the  left  side  of  the  body,  under  the 
edge  of  the  little  saddle-like  rudimental  shell,  which 
in  this  mollusc  is  enclosed  in  the  mantle. 

The  heads  of  univalve  molluscs  bear  several 
organs  of  sense,  tentacles,  eyes  and  ear  sacs,  the 
tentacles  are  long  soft  feelers,  the  '  horns '  of  the  snail, 
which  can  be  retracted  by  being  involuted,  or  turned 
out-side  in  by  muscles.  In  the  common  snail  the 
eyes  are  placed  on  the  extremities  of  the  upper  or 
longest  pair  of  horns,  and  can  be  seen  as  bright  black 
spots.  In  other  molluscs  the  eyes  are  either  stalked 
or  placed  at  the  bases  of  the  tentacles.  The  organs 
of  hearing  are  small  sacs  placed  near  the  foot, 
filled  with  fluid  and  containing  small  concretions. 
Most  univalve  molluscs  lay  their  eggs  inside  little 
cases  often  to  be  met  with  under  stones  on  the  sea- 
shore. The  little  ciliated  larva  has  a  shell  even  at  its 
earliest  stage,  and  in  some  molluscs  this  shell  is  lost  in 
development ;  in  others  it  is  retained  and  can  be 
seen  at  the  tip  of  the  adult  shell  as  the  'nucleus.' 

Classification. — The  head-bearing  molluscs  are 
very  numerous,  and  are  divided  into  several  sub- 
classes. The  first  of  these  includes  the  little  ele- 
phant's-tooth  shells,. or  Dentalinm.  This  animal  has 
no  heart,  and  is  completely  enclosed  in  its  mantle, 
which  in  the  embryo  forms  at  first  a  minute  two- 
valved  shell.  Eventually,  however,  this  shell  becomes 
tubular,  open  at  both  ends.  The  second  sub-class 
consists  of  small  molluscs  found  swimming  in  the 
ocean,  by  means  of  two  large  wing-like  processes  on 
the  upper  part  of  their  foot,  and  hence  are  named 


Sense  Organs  of  Molluscs,  89 

Pteropoda.  The  third  sub-class  includes  all  the  re- 
maining forms,  a  few  of  which  are  free,  swimming 
with  the  foot  flattened  into  a  screw-propeller.  Most 
of  them  crawl  on  the  under  surface  of  their  body,  and 
hence  are  called  Gasteropoda.  Among  these,  a  large 
number  are  branchiateTor  gill-breathing ;  these  make 
up  one  order ;  the  others  are  pulmonate  or  air-breath- 
ing, and  make  up  a  second  order.  The  branchiate 
forms  have  the  gills  either  in  front  of  the  heart  or  else 
behind  the  heart,  as  in  the  great  group  of  shell  less 
naked-gilled  molluscs  like  the  Doris  or  yEolis,  so  com- 
mon on  the  shore.  Some  of  the  former  sub-order 
have  shells  of  eight  valves,  like  the  common  Chiton ; 
others  have  the  gills  all  round  the  body,  under  the 
mantle,  and  equal  on  both  sides,  as  in  the  limpets, 
or  they  may  be  unsymmetrical  as  in  the  ear-shells, 
cones,  shoulder  of-mutton  shells,  etc. 

Snails.  — The  air-breathing  order  are  the  land  shells 
or  snails ;  they  have  their  breathing  chamber  placed 
behind  the  heart,  and  the  larva  has  in  general  a  very 
rudimental  ciliary  lobe.  A  curious  difference  has 
been  noted  between  the  gill -bearing  and  lung-bearing 
molluscs,  namely,  that  the  intestinal  tube  is  bent 
towards  the  haemal  side  of  the  body,  that  is,  towards 
the  heart,  in  the  former,  while  it  is  turned  towards 
the  nerve-ganglion  in  the  latter. 


9O  Invertcbrata. 


CHAPTER  XVII. 

CUTTLEFISHES. 

CLASS  IV.  Cephalopoda. — The  highest  class  of  mol- 
luscs is  that  which  consists  of  Nautili,  Cuttlefishes  and 
Squids.  These  are  all  highly  organised  marine  animals 
with  a  central  mouth,  around  which  there  are  processes 
of  the  foot,  disposed  in  the  form  of  a  circlet  of  arms 
or  tentacles  ;  each  of  these  arms  is  provided  with  one 
or  more  rows  of  large  suckers,  and  thus  they  form  a 
powerful  grasping  organ,  which  they  use  in  taking  the 
prey  whereupon  they  feed. 

Shells. — Very  few  of  these  are  enveloped  in  shells, 
and  most  of  them  progress,  when  creeping,  with  the 
head  down,  and  with  the  large  mantle  cavity  at  the 
hinder  side.  There  are  three  kinds  of  shells  found 
clothing,  or  contained  in,  some  animals  of  this  class. 
These  are  ist.  The  chambered  shell,  such  as  that  of 
the  pearly  nautilus  (fig.  54,  p.  92),  a  coiled  spiral 
divided  by  numerous  partitions  into  successive  cham- 
bers (/;),  each  of  which,  however,  communicates  with 
the  neighbouring  chambers  by  means  of  a  tube  or 
siphuncle  (c).  2.  The  enclosed  shell,  a  horny  or  calca- 
reous plate  or  oval  mass,  embedded  in  the  integu- 
ment, or  lying  in  a  closed  cavity  along  the  front 
wall  of  the  animal's  body ;  such  a  shell  is  found  in 
the  cuttlefish  and  squid.  3.  In  one  species  there 
is  a  singular  shell  secreted  by  two  of  the  arms 
which  lie  beside  the  mouth,  and  which  are  flattened 
organs,  and  the  shell  so  secreted  is  a  slightly  spiral 


Cuttlefishes. 

FIG.  53. 


Cuttlefish  or  Sepia,     c.  Arms  bearing  the  suckers  ;   d,  long  tentacle-like 
arms  ;  a,  mantle  ;  b,  lateral  fins  ;  e,  eyes. 


92  Invertcbrata. 

rapidly  expanding  shell  of  a  delicate  paper-like  texture 
to  which  the  'name  '  paper  nautilus '  or  Argonaut  has 

FIG.  54. 


been  given.     Other  species,  like  the  Octopus  or  sea- 
spider,  have  no  shell  either  internal  or  external. 

Anatomy. — On  account  of  the  fore-shortening  of 


Anatomy  of  Cuttlefishes.  93 

the  body  the  mouth  is  brought  into  the  middle  ol 
the  foot  in  the  adult,  and  hence  the  name  'head- 
footed'  {Cephalopoda)  given  to  this  class.  The  lobes 
into  which  the  foot  is  divided  are  usually  eight  or 
ten  in  number  and  are  long  tapering  muscular  pro- 
cesses which  in  the  common  species  in  our  own  seas 
vary  from  a  few  inches  to  two  feet  in  length,  but  in 
one  rare  form  they  attain  very  much  greater  size. 
During  the  year  1873,  a  specimen  was  captured  on 
the  Newfoundland  coast,  with  arms  forty-two  feet  long. 

The  mouth  is  furnished  with  a  strong  beak,  like 
that  of  a  parrot,  with  two  formidable  horny  jaws.  By 
reason  of  the  numerous  suckers  on  the  arms  (a  com- 
mon octopus  possessing  about  60  on  each  arm), 
which  seize  hold  of  their  prey  with  a  cupping-glass- 
like  tenacity,  these  cuttlefishes  are  among  the  most 
terrible  of  marine  monsters,  and  those  of  large  size 
would  probably  prove  to  be  more  than  a  match  even 
for  man  himself. 

Each  of  the  sucking  disks  is  singularly  perfect  in 
its  structure.  There  is  a  muscular  adhesive  disk  of  a 
circular  shape,  around  whose  edge  is  a  hard  crown  of 
horny  consistence,  and  in  the  centre  there  is  a  mus- 
cular retractile  piston,  whose  contraction  produces  a 
vacuum,  and  thus  causes  a  close  adhesion  of  the  sucker. 

There  is  a  large  mantle  cavity  with  a  strong  mus- 
cular wall.  When  the  animal  is  swimming  it  moves 
with  its  arms  directed  backwards  and  the  upper  or 
pointed  end  of  the  body  forwards;  in  this  position  the 
opening  of  the  mantle  cavity  or  funnel  is  directed 
backwards,  and  the  propulsive  force  which  drives  the 
body  forwards  is  the  sudden  and  often  repeated  con- 


94  Invertebrata. 

traction  of  the  wall  of  this  cavity,  which  by  driving  a 
column  of  water  in  the  opposite  direction  with  great 
force,  propels  the  creature  by  rhythmical  jerks,  and  at 
a  rapid  rate. 

On  slitting  open  the  mantle  two  large  gills  are 
seen,  one  on  each  side,  above  and  between  which  is 
the  heart-ventricle.  The  blood  enters  the  gills  by 
large  veins  which  form  dilatations  at  the  base  of  these 
breathing  organs,  then  after  being  aerated,  it  is  col- 
lected in  two  cavities  called  systemic  auricles,  from 
whence  it  passes  into  the  muscular  ventricle  which 
drives  it  through  the  arteries  into  the  lacunae  (or  tissue 
interspaces  of  the  body). 

Along  the  hinder  edge  of  the  long  digestive  canal 
there  is  a  slender  tube,  whose  opening  is  also  at  or 
near  the  mouth  of  the  funnel,  and  whose  upper  end 
expands  into  a  large  spongy- walled  sac  lying  close 
beside  the  liver.  This  sac  secretes  a  brown  or  black 
inky  material  which  is  poured  out  in  enormous  quan- 
tities when  the  animal  is  pursued,  and  which  by  ren- 
dering the  water  opaque  covers  the  flight  of  the 
cuttlefish. 

At  the  mouth  of  the  mantle-cavity  but  not  actually 
connected  with  it  there  is  a  funnel,  which  when  the 
margin  of  the  mantle  contracts  forms  a  narrow  tubular 
outlet  for  the  fluid  of  the  cavity. 

Cuttlefishes  possess  a  brain,  made  up  of  large 
confluent  ganglia  around  the  pharynx,  and  over  this 
there  is  a  cartilaginous  cover,  interesting  as  being  one 
of  the  first  signs  of  an  internal  skeleton,  like  that  of 
vertebrates  in  the  animal  kingdom.  There  is  also  a 
large  and  complex  eye,  more  like  that  of  a  vertebrate 


Anatomy  of  Cuttlefishes.  95 

animal  than  is  the  eye  of  any  other  group  of  inverte- 
brates. 

Cephalopods  were  abundant  in  former  ages,  but 
there  are  now  about  230  species  living;  of  these  the 
Nautili  possess  a  chambered  shell,  four  gills,  and 
many  tentacles,  while  all  others  have  only  two  gills, 
and  eight  or  ten  sucker-bearing  arms. 

Recapitulation. — Having  thus  very  briefly  re- 
viewed the  sub-kingdom  Mollusca,  we  may,  by  way  of 
recapitulation,  place  in  a  tabular  form  the  distinctive 
characters  of  the  group  and  its  divisions.  They  are 
all  soft-bodied,  never  distinctly  divided  into  segments 
nor  provided  with  jointed  limbs  ;  enveloped  more  or 
less  in  a  dermal  mantle,  which  often  secretes  a  shell, 
and  their  larval  stage  is  usually  ciliated,  worm-like. 

The  divisions  are : 

A.  Having  no  distinct  head,  bivalve  shells  with  the 

valves  dorsal  and  ventral ;  no  separate  gills  = 
Class  I.  Brachiopoda. 

B.  Having  no  distinct  head,  bivalve  shells  with  the 

valves  right  and  left,  gills  lamellar  =  Class  II. 
Lamellibranchiata  or  Acephala. 

C.  Having  a  distinct  head,  univalve  shells  (at  some 

period   of   existence)  =  Class    III.    Cephalo- 
phora. 

a.  Entirely  enclosed  in  a  mantle,  secreting  a 

tubular  shell  =  Sub-class  I.  Scapho- 
poda  (Dentalium). 

b.  Not  entirely  enclosed  in  a  mantle,  swim- 

ming by  finlike  processes  on  the  upper 
side  of  the  foot  =  Sub-class  II. 
Pteropoda. 


Invertebrata. 

c.  Creeping  by  the  foot  or  swimming,  but 

not  by  finlike  processes  =  Subclass 
III.  Gasteropoda. 

d.  Having  the  foot  around  the  head,  and 

modified  either  into  tentacles  or 
sucker-bearing  arms  =  Class  IV. 
Cephalopoda. 


CHAPTER   XVIII. 

SHE-KINGDOM  VII.    ARTHROPODA  (JOINTED  ANIMALS). 

General    Characters. — This    sub-kingdom    includes 
those  animals  whose  bodies  are  furnished  with  an  ex- 
F  ternal  hard  protective  layer,  and  which 

bear  jointed  limbs  appended  to  each 
segment  of  the  body  (fig.  55).  The 
armour-plating  of  the  body  is  known 
by  the  name  exoskeleton,  to  distinguish 
it  from  the  bones,  which  form  the  axis 
of  support  for  vertebrate  animals,  to 
^{^  tne  name  endoskelcton  is  given. 
The  exo- skeleton  consists  of  chitin,  a 
horny  substance,  which  is  capable  of  resisting  all  re- 
agents except  the  most  powerful  corrosives.  This 
layer  is  usually  coloured,  laminated,  and  to  the  micro- 
scope shows  very  little  structure  except  the  numerous 
fine  canals  which  pierce  it  from  within,  to  which  the 
name  pore-canals  is  given. 

The  body  of  an  arthropod   consists  of  a   chain 
of  segments,  all  built  on  a  common  pattern,  and  each 


Jointed  A  nimals.  97 

one  strengthened  by  the  possession  of  a  ring  of  exo- 
skeleton  consisting  of  two  parts,  a  dorsal,  and  a 
ventral  half  arch.  The  limbs  are  articulated  on  each 
side,  between  the  half  arches,  each  segment  possessing 
one  pair.  These  generally  remain  distinct,  even  when, 
the  segments,  as  often  happens,  fuse  together,  so  that 
the  number  of  constituent  segments  can  be  very  often 
detected  from  the  limbs,  even  when  the  body  rings 
are  .united  into  a  continuous  shield. 

The  bodies  of  arthropods  are  bilaterally  symme- 
trical. They  are  also  remarkable  for  the  absence  of 
cilia  at  all  periods  of  life. 

Each  limb  consists  of  several  joints,  each  having 
an  external  chitinous  exoskeleton,  containing  the 
muscles  which  move  it.  In  the  simplest  arthropods, 
the  limb  consists  of  a  basal  segment  bearing  two 
appendages,  an  outer  and  an  inner.  In  the  higher 
forms  the  limbs  are  divided  into  five,  seven,  or  more 
joints.  These  limbs  are  used  for  various  purposes, 
becoming  modified  into  feelers,  water-bailers,  jaws, 
swimmers,  pincers,  or  walking  feet 

All  arthropods  have  a  circulatory  system  and  most 
of  them  possess  a  heart  which  is  a  dorsal  tube,  divided 
by  valves  into  successive  chambers,  but  there  are 
rarely  fine  blood  vessels.  There  is  a  distinct  respira- 
tory system,  and  a  complex  digestive  canal,  except  in 
parasitic  forms,  and  they  have  all  a  symmetrical  ner- 
vous system,  consisting  of  two  ganglia,  one  above,  the 
other  below  the  throat,  followed  by  a  chain  of  ganglia 
in  the  ventral  portion  of  the  body.  They  are  divided 
into  four  great  classes,  i.  Crustacea,  including  all 
those  that  breathe  by  gills,  as  crabs,  lobsters,  &c. ; 

H 


98  Invertebrata. 

2.  Arachnoidea,  spiders,  mites,  and  scorpions ;  3. 
Myriopoda,  centipedes,  &c.,  4.  Jnse:ta. 

Many  arthropods  are  parasitic,  and  these  are  at 
first  not  unlike  allied  non-parasitic  species,  but 
shortly  after  hatching  they  retrogress,  such  parts  as 
are  not  necessary  disappear  and  hence  the  adult 
parasites  are  in  their  organisation  much,  simpler  even 
than  they  themselves  were  in  their  embryonic  states  ; 
but  as  has  been  already  noticed,  the  egg-producing 
organs  are  much  increased  in  development. 

From  two  to  six  of  the  foremost  segments  of  the 
body  in  arthropods  become  united  to  make  up  a  head, 
which  carries  sentient  organs,  such  as  the  eyes,  ears, 
and  antennae  or  feelers,  with  the  mouth.  In  the  head 
likewise  is  the  large  supraoesophageal  nerve-ganglion  or 
brain,  which  sometimes  is  large  and  complex,  as  in  ants. 


CHAPTER  XIX. 

CRABS   AND    LOBSTERS. 

CLASS  I.  Crustacea. — The  animals  of  this  class  are 
all  water-breathers,  either  provided  with  gills,  or  else 
with  a  thin  integument  through  which  the  blood 
becomes  directly  aerated.  The  structure  of  a  crustacean 
can  be  easily  understood  by  examining  a  lobster  or 
freshwater  crayfish.  In  either  of  these  we  notice  that 
the  body  is  divided  into  two  regions,  an  anterior, 
covered  by  a  dorsal  shield  of  two  pieces,  and  a 
posterior,  consisting  of  a  series  of  rings,  ending  in 
the  fan-like  tail.  In  the  body  of  the  lobster  we  notice 


Segments  of  a  Lobster. 


99 


FIG.  56. 


three  openings, — the  mouth,  the  terminal  opening 
of  the  digestive  canal  in  the  middle  line  of  the  last 
joint  of  the  tail  on  the  under  surface,  and  the  open- 
ing of  the  egg-producing  organs  at  the  base  of  the 
third  pair  of  walking  limbs.  Through  this  last  the 
eggs  are  extruded,  and  are  carried  in  clusters  under 
and  around  the  bases  of  the  hind  series  of  feet 

In  the  large  anterior  mass  of  the  body,  sheltered 
by  the  dorsal  shield,  there  are  fourteen  segments 
united,  comprising  the  head, 
thorax,  and  abdomen.  The 
head  segments  bear  their  six 
pairs  of  appended  limbs,  the 
first  pair  of  which  are  modi- 
fied into  stalks  for  the  eyes, 
which  are  remarkable  organs, 
each  consisting  of  a  large 
number  of  rods  of  a  crystal- 
line appearance,  each  placed 
at  the  end  of  a  nerve  fibril  or 
thread,  and  surrounded 
by  a  mass  of  pigment  The  numerous  united  fibrils 
of  the  optic  nerve  pass  in  the  centre  of  the  stalk, 
and  each  fibril  ends  in  its  crystal  rod,  the  mass  of 
rods  being  arranged  in  a  cluster,  slightly  divergent 
so  as  to  exhibit  a  rounded  outer  surface,  over  which 
the  chitinous  skin  extends  as  a  fine,  perfectly  trans- 
parent covering. 

The  second  pair  of  limbs  are  feelers  called  the 
antennules  or  lesser  antennae,  consisting  of  three 
basal  joints,  terminated  by  a  pair  of  slender  processes 
each  made  up  of  many  little  rings ;  these  are  followed 


Vertical  section  through  the  eye 
of  an  Insect,  showing  the  stalk 
or  optic  nerve,  the  white  radiat- 
ing lines  or  secondary  optic 
nerves  and  the  crystal  cones. 


H  2 


IOO  Invertebrata. 

by  the  third  pair  of  limbs,  or  the  large  antennae,  con- 
sisting of  five  basal  joints  succeeded  by  a  long  feeler. 
The  bases  of  the  fourth  pair  of  limbs  are  modified  into 
biting-jaws  or  mandibles,  and  they  bear  an  internal 
appendage  named  the  mandibular  palp.  The  fifth 
and  sixth  pairs  of  limbs  are  also  jaws,  and  are  called 
maxillae ;  they  also  bear  rudimental  appendages.  The 
three  segments  that  follow  the  head  segments,  and 
are  united  thereto,  make  up  the  thorax,  and  their 
limbs  are  also  in  the  lobster  modified  into  organs  of 
mastication,  and  hence  are  known  by  the  name  of 
foot-jaws;  each  of  these  except  the  first  bears  outer 
and  inner  appendages,  but  the  third  pair  is  of  very 
little  use  as  a  chewing  organ,  but  bears  a  gill  as  does 
also  its  anterior  neighbour,  the  second  pair  of  foot  jaws. 
Following  the  limbs  of  the  cephalo-thorax,  for  so 
the  united  head  and  thorax  is  often  called,  we  come 
to  five  pairs  of  walking  legs,  each  pair  being  the  limbs 
borne  by  a  segment  of  the  abdomen.  These  five 
abdominal  segments  are  also  in  the  lobster  covered 
over  dorsally  by  the  dorsal  shell,  but  on  the  under 
or  ventral  surface,  their  separateness  can  be  very  well 
recognised.  The  first  pair  of  limbs  consist  of  the 
pincers  or  chela.  These  formidable  organs  in  the 
lobster  are  made  up  of  seven  joints,  the  last  but  one 
of  these  is  very  large,  and  its  outer  angle  is  prolonged 
into  a  finger-like  process  capable  of  being  opposed 
to  the  last  joint,  thus  making  a  grasping  organ  of 
great  power.  In  the  lobster  the  two  pincers  are  not 
quite  symmetrical ;  one  is  armed  along  the  edges  of 
the  blades  of  the  pincers  with  rough  tubercles,  the 
other  with  small  serratures ;  the  former  claw  is  prob- 


Lobsters  and  Crabs.  101 

ably  used  as  an  anchoring  apparatus,  die,  latter  for 
seizing  articles  of  food. 

The  two  succeeding  pairs  of  abdominal  km  15s-  rtfe 
also  pincer-like  at  the  extremity ;  the  two  following 
are  simply  pointed,  but  still  exhibit  seven  joints.  All 
the  abdominal  limbs,  except  the  last,  carry  gills  ap- 
pended to  the  basal  joint,  and  placed  under  cover  of 
the  dorsal  shell. 

The  six  movable  rings  which  form  the  '  tail '  of 
the  lobster,  bear  laterally  limbs  adapted  for  swimming, 
each  made  up  of  a  basal  part,  and  two  flattened 
appendages  external  and  internal;  the  last  of  these 
segments  not  only  carries  the  widely  expanded 
swimmer  or  tail  fins,  but  bears  at  its  hinder  extremity 
also  a  single  median  flap  or  'telson/  sometimes 
regarded  as  a  separate  segment  These  movable  rings 
make  up  the  post-abdomen. 

The  ear  in  the  lobster  is  a  sac  at  the  base  of  the 
antennule ;  the  gills  lie  under  the  hinder  and  lateral 
parts  of  the  dorsal  shield.  The  stomach  is  a  gizzard- 
like  cavity  with  calcareous  masses  lining  its  walls, 
followed  by  a  narrow  soft-walled  digestive  stomach 
and  intestine,  below  which  lies  the  nerve-cord,  and 
above  it  is  the  heart. 

The  crab  differs  from  the  lobster  not  only  in  shape 
but  in  the  comparative  immobility  and  small  size 
of  its  abdomen,  which  is  turned  in  and  sunk  into 
a  groove.  While  the  young  lobster  only  differs  from 
the  adult  in  the  possession  of  small  outer  appendages 
on  the  walking  limbs,  and  the  smaller  size  of  the  tail, 
the  crab  emerges  from  the  egg  in  a  form  utterly 
unlike  the  adult,  as  a  little  swimming  creature  with 


102 


Invertebrata. 


a  d6r£a|  jsjhtiel$  armed  with  a  strong  median  spine 
(fig.  57,  A)  arid  followed  by  a  jointed  abdomen  which 
:  Jie&fs  aiop  appended  limbs. 

A  closely  allied  animal  common  on  our  shores 
is  the  hermit  crab,  which  protects  its  soft,  almost 
limbless  abdomen  by  inserting  it  into  the  deserted 
shell  of  a  whelk,  or  other  univalve  mollusc.  In  these 

FIG.  57- 


Stages  in  the  development  of  the  common  Shore  Crab  (Carcinus  manas). 
A,  First  or  zoea  stage  ;  B,  early  stage  with  tail ;  c,  D,  advanced  stages 
of  growth. 

the  pincers  are  usually  unequal,  so  that  on  the 
animal  being  molested,  one  can  be  retracted  while 
the  larger  one  blocks  up  the  passage.  The  soft 
abdomen  acts  as  a  sucker,  whereby  the  hermit  crab 
retains  its  hold  on  its  habitation. 

There  are  many  varieties  of  form  among  Crustacea, 
and  those  above  described  are  among  the  most  highly 
organised,  all  having  stalked  eyes  and  ten  walking 
feet.  The  mantis  shrimps  have  their  thoracic  limbs 
fitted  for  walking,  as  well  as  the  abdominal  legs,  so 
that  instead  of  ten,  there  are  fourteen  or  sixteen  legs. 


Small  Crustaceans.  103 

All  these  forms  make  up  a  sub-class  of  Crustacea  named 
Podophthalmia  on  account  of  their  stalked  eyes. 

The  sand-hoppers  (fig.  55),  wood-lice,  and  fresh- 
water shrimps,  make  up  a  second  sub-class,  charac- 
terised by  possessing  sessile  eyes.  These  also  have 
bodies  made  up  of  twenty  segments,  each  of  which, 
except  those  of  the  head  and  thorax,  has  its  own  in- 
dependent chitinous  ring,  and  the  two  hinder  pairs  of 
foot-jaws  are  used  for  locomotion.  Some  of  these, 
like  the  sand-hoppers  and  freshwater  shrimps,  have  the 
three  hindmost  pairs  of  abdominal  feet  arranged  so  that 
their  joints  bend  forwards  while  all  the  other  limbs 
bend  with  their  joints  concave  backwards.  These  are 
called  Amphipoda,  to  distinguish  them  from  those  like 
the  wood-lice,  and  slaters,  whose  legs  are  all  directed 
one  way,  which  are  called  Jsopoda. 

The  king  crabs  of  the  Mollucca  Islands  and  of 
North  America  form  the  types  of  a  third  sub-class. 
They  resemble  the  lobster  in  having  the  head,  thorax, 
and  abdomen  covered  by  a  great  dorsal  buckler,  but 
differ  in  that  there  are  six  walking  limbs  around  the 
mouth,  whose  bases  are  spiny,  and  compressed, 
acting  as  jaws.  The  eyes  are  not  stalked-,  and  there 
is  a  long  bayonet-shaped  tail,  behind  the  abdomen, 
corresponding  to  the  telson  of  the  lobster.  The  seg- 
ments of  the  abdomen  are  faintly  marked  in  the  adult 
king  crab. 

In  the  past  ages  of  the  world,  larger  allied  forms 
existed  abundantly  ;  other  allied  fossil  forms  had  three- 
lobed  bodies,  and  hence  are  known  as  Trilobites,  and 
they  are  only  found  in  palaeozoic  rocks.  In  stagnant 
pools  of  fresh  water  little  creatures  called  water  fleas 


IO4  Invertebrata. 

can  be  seen,  by  the  aid  of  the  microscope,  actively 
darting  about ;  these  are  representatives  of  a  fourth 

sub-class.    They  are  all 
FlG-  s8.  minute  at  the  present 

day.  Certain  forms 
bear  gill  processes  ap- 
pended to  their  feet, 
and  hence  are  known 
as  '  gill-footed '  or  Bran- 
chiopods.  Many  close- 
ly allied  species  have 
the  dorsal  wall  extend- 

Cyclopsquadricornis  carrying  its  egg  sacs.   e(J  jn  the  form  of  an  en- 
o.  he  small  figure  is  the  Nauphus  or  larva. 

veloping  shell,  just  like 
the  gill-covering  laminae  in  the  lobster. 

Those  crustaceans  which  are  parasitic  are  closely 
related  to  the  water  fleas,  and  undergo  retrogression 
until  they  become  reduced  to  little  sacs  with  bristles 
for  jaws,  with  sucker-like  fore  feet,  and  often  with  no 
trace  of  segmentation  (fig.  59,  A).  Some  live  on  the 
bodies  of  larger  crustaceans  such  as  lobsters,  others 
on  tunicates,  but  they  are  mostly  found  attached  about 
the  gills  of  fishes.  The  early  stages  of  .these  are  little, 
free,  marine  larvae  with  developed  jaws  and  a  moderate 
post-abdomen  (fig.  58).  Many  non-parasitic  species 
remain  for  their  whole  life  in  a  state  like  that  of  the 
larvse  of  these  parasites. 

In  all  these  lower  crustaceans  the  earliest  stage 
of  existence  after  emission  from  the  egg  is  in  the 
form  of  a  minute  oval  body  with  three  pairs  of  limbs 
and  one  central  eye.  This  is  known  as  a  Nauplius, 
and  it  assumes  its  adult  form  by  the  growth  of  new 
segments  and  new  limbs.  The  nauplius  stage  of 


Metamorphoses  of  Cmstaceans.  105 

higher  crustaceans  is  transitory,  and  sometimes  is 
passed  over  before  the  embryo  leaves  the  egg,  and  in 
crabs  the  form  assumed  by  the  newly  hatched  young 
is  that  of  a  small  shield-covered  body  with  two  eyes 
and  long  jointed  abdomen  (fig.  57,  A)  ;  this  curi- 
ous larva  is  called  Zoea,  and  by  the  shortening  of  its 

FIG.  59. 


Pennella,  parasitic  on  the  Sunfish.      A,  Entire  animal, 
half  real  size  ;  B,  head. 

tail  and  the  vanishing  of  its  dorsal  spine,  it  becomes 
changed  into  its  adult  form. 

All  crustaceans  undergo  successive  moultings  or 
changings  of  shell,  and  during  these  changes  lost  parts 
become  restored  and  the  several  changes  in  meta- 
morphosis can  be  seen  at  these  periods.  Crustaceans 
part  with  their  limbs  easily  under  circumstances  of 
fright  or  seizure  ;  thus  if  a  limb  be  taken  hold  of 
forcibly  the  animal  will  probably  break  it  off  between 
the  first  and  second  joints  in  its  efforts  after  freedom. 
At  the  next  moult,  there  appears  a  new  limb  budding 
on  the  soft  uncovered  body,  and  when  the  new  shell 
forms  and  hardens,  a  small  limb  is  seen  in  place  of 
the  lost  one. 


Io6  Invertebrata. 

Some  of  the  metamorphoses  of  crustaceans  are 
strange ;  in  none  more  so  than  in  the  barnacles  and 
acorn- shells  (figs.  4  and  5,  pp.  9  and  10),  the  lowest 
subclass  of  the  series.  Acorn-shells  or  Balani,  are  the 
little  limpet-like  shells  which  encrust  the  rocks  along 
all  our  coasts  and  which  can  be  at  once  recognised  by 
the  opening  at  the  top  of  the  conical  shell,  which  is 
closed  by  the  lateral  valve-like  or  beak-like  plates. 
Barnacles  are  commonly  found  adhering  to  logs  of 
wood  or  to  ships'  bottoms.  These  begin  life  as  active 
nauplius-like  larvae,  which  every  autumn  are  to  be 
found  swimming  along  our  coasts.  This  larva  at  its 
early  moults  develops  a  lateral  mantle-fold.  At  its 
fourth  change  in  shell,  the  front  of  its  head  becomes 
fixed  by  the  flattening  of  one  of  the  joints  of  the 
antennse  and  by  the  secretion  poured  out  by  a  gland 
which,  though  placed  in  the  body,  has  its  duct  open- 
ing in  the  altered  joint  of  the  antennae.  At  the  fifth 
moult  the  eyes  and  antennse  vanish,  the  head  becomes 
fixed  by  a  broad  base  of  attachment,  the  mantle-like 
fold  of  integument  surrounds  the  body  and  becomes 
calcified  into  a  shell  of  many  valves,  within  which  the 
hinder  parts  of  the  body  are  enclosed  together  with 
their  six  pairs  of  limbs.  These  limbs  remain  free 
and  capable  of  slight  protusion,  while  the  mouth 
with  its  mandibles  lies  at  the  bottom  of  the  mantle 
cavity. 

Some  Balani  select  curious  places  of  residence. 
Coronula  lives  on  the  skin  of  the  whale ;  Anelasma 
often  is  adherent  to  fishes,  and  many  others  to  corals. 
One  closely  allied  group  of  degraded  forms  are  para- 
sites on  the  abdomen  of  crabs.  To  the  sub-class 


Classes  of  Crustaceans.  1 07 

comprising  all  these  forms  the  name  Cirripedia,  or 
tentacle-footed,  has  been  given. 

Recapitulation. — We  have  thus  seen  that  the 
seven  classes  of  water-breathing,  many-jointed  forms 
which  make  up  the  class  Crustacea  are  very  dissimilar 
in  details.  They  may  be  arranged  in  a  tabular  series 
as  follows : — 

A.  Sessile  Crustaceans,  often  pseudo-parasitic,  usually 

enclosed  in  a  many  valved  shell  =  Sub-class  I. 
Cirripedia. 

B.  Free,  with  a  cephalo-thorax  and  two  pairs  of  tho- 

racic limbs,  none  of  the  feet  bearing  gills  = 
Sub-class  II.  Copepoda  (fig.  58). 

C.  Free,  with  the  body  enclosed  in  a  bivalve  shell 

made   of  the   extended  dorsal    integument  = 
Sub-class  III.  Ostracoda. 

D.  Free,  with   no   enclosing  shell,   feet  gill-bearing, 

segments  less  or  more  than  twenty  =  Sub-class 
IV.  Branchiopoda. 

E.  Free,  with  a  large  cephalo-thorax,  small  walking 

limbs,  six  pair  of  which  are  arranged  around  the 
mouth = Sub-class  V.  Pcecilopoda.     King  Crabs. 

F.  Free,  with  a  cephalo-thorax,  stalked  eyes  and  a 

body    of   twenty    segments  =  Sub-class    VI. 

Podophthalmia. 

A.  Thoracic  limbs  masticatory,  ten  abdominal 

limbs  alone  fitted    for  walking  =  Order  I. 

Decapoda. 

a.  With   a   long   abdomen  :  Lobsters  = 

Sub-order  I.  Macrura. 

b.  With  a  soft  limbless  abdomen :  Her- 

mit  Crabs  =  Sub-order    II.      Ano- 
mura. 


1 08  Invertebrata. 

c.  With    a    short    up-turned    abdomen : 

Crabs  =  Sub-order  III.  Brachyura. 
B.  Some  thoracic  limbs  ambulatory,  thus  mak- 
ing twelve,  fourteen,  or  sixteen  pairs  of 
walking  limbs  =  Order  II.  Stomapoda. 
G.  Free,  with  a  cephalo-thorax,  twenty  segments  and 
sessile  eyes  =  Sub-class  I.  Edriophthalmia. 


CHAPTER  XX. 

SPIDERS    AND     MITES. 

CLASS  II.  Arachnoidea. — These  are  terrestrial  air- 
breathing  creatures  in  which  the  segments  that  com- 
pose the  head  and  thorax  are  united  to  form  a  single 
cephalo-thorax,  but  their  articulated  limbs  are  to  some 
extent  represented,  and  of  these,  four  pairs  are  usually 
used  in  walking.  There  is  an  abdomen  with  a  variable 
number  of  rings.  Whenever  eyes  are  present  they  are 
not  compound  bundles  of  crystal  rods  covered  by  a 
common  cornea,  as  in  crustaceans,  but  they  consist  of 
separate  transparent  cones  surrounded  with  pigment 
and  always  few  in  number.  There  are  never  any 
antennae  developed  as  such,  but  the  mandibles  are 
always  present,  and,  in  scorpions,  the  maxillary  palps 
form  pincers  or  claws  like  those  of  a  crab  ;  such  claws 
are  called  chelicera.  The  second  pair  of  maxillary 
palps  form  the  first  pair  of  walking  limbs,  while  the 
first  and  second  pairs  of  thoracic  limbs,  as  seen  in  the 
true  insects,  are  developed  as  the  second  and  third 
pairs  of  legs,  and  the  third  pair  of  thoracic  limbs  is 
absent ;  at  the  base  of  the  abdomen  is  a  curious  pair 


Spiders  and  Mites.  109 

of  comb-like  organs  in  the  scorpion.  The  parts  of 
each  limb  are  like  those  in  Crustacea ;  the  body  and 
its  organs  are  however  much  shorter  than  in  that  class. 
The  nervous  system  is  concentrated,  the  digestive 
canal  often  has  blind  pouches  appended  to  it.  There 
is  an  abdominal  heart  in  all,  except  in  a  few  mites, 
•and  there  is  usually  a  series  of  breathing  tubes.  Or- 
gans of  touch,  smell  and  hearing  seem  to  be  de- 
ficient. 

Many  of  these  animals  are  parasites,  either  ex- 
ternal, or  internal ;  but  except  in  these,  there  are  few 
in  which  the  young  undergo  much  metamorphosis 
after  hatching. 

The  outer  surface  is  often  hard  and  chitinous,  but 
never  calcined.  The  dorsal  surface  layer  is  seldom 
extended  over  any  of  the  neighbouring  segments  or 
appendages,  or  when  extended  it  is  immovable. 

Mites. — The  three  orders  in  the  class  consist  of 
mites,  spiders  and  scorpions.  Of  these  the  mites  are  the 
simplest  and  are  exemplified  by  the  cheese-  FlG. 
mite,  found  in  mouldy  cheese,  or  the 
sugar-mite  often  met  with  in  brown  sugar. 
In  these  the  abdomen  is  unsegmented, 
and  usually  indistinctly  separate  from  the 
cephalo-thorax.  The  breathing  organs 
are  fine  tubes  named  tracheae,  which  open 
on  the  surface,  and  break  up  within  the 
body  into  branches,  which  admit  air  into  the  tissues. 
The  mouth  in  mites  is  often  proboscis-like  or  armed 
with  a  spiny  beak.  Most  of  them  are  parasites  either 
upon  animals  or  plants.  One  curious  group  inhabits 
the  body  cavities  of  vertebrate  animals,  wherein  their 
worm-like  bodies  may  be  mistaken  for  tape-  or  thorn- 


HO  Invertebrata. 

headed-worms.  They  are  however  easily  distinguished 
by  their  embryos  bearing  true  jointed  limbs,  although 
these  are  lost  in  the  adults. 

One  form  has  been  found  in  the  contents  of  the 
small  fat  glands  on  the  human  face,  and  another  is 
the  cause  of  the  disgusting  skin  disease  known  as 
'  itch/  Other  larger  forms  are  the  '  ticks '  found  so 
commonly  on  sheep,  dogs,  bats,  camels,  &c.  Of 
non-parasitic  forms,  the  little  ' red-spider'  so  often 
seen  on  the  sea-shore  under  stones  between  tide- 
marks,  and  the  '  glass- '  and  '  garden-mites '  found  in 
damp  moss  and  among  vegetables  are  examples. 

Spiders. — In  spiders  the  cephalo-thorax  is  joined  to 
the  sac-like  abdomen  by  a  narrow  stalk,  and  the  latter 
portion  never  bears  any  limb-processes.  The  tracheae, 
instead  of  being  bundles  of  branching  tubes,  are  con- 
densed and  flattened,  and  included  in  definite  spaces, 
in  which  the  compressed  tubes  look  like  the  leaves  of 
FIG.  61.  a  book,  the  whole  laminated  organ  on 
account  of  its  being  circumscribed  and 
lung-like,  is  called  a  tracheal-lung,  and 
the  spiders  are  often  called  pulmonary 
arachnoids  on  account  of  their  possess- 
ing these  organs. 

Spiders  have  little  clusters  of  simple 
eyes  on  their  foreheads,  bright  small 
specks  usually  eight  in  number  and 
generally  arranged  in  two  rows.  The 
mandibles  have  at  their  inner  side 

Scorpion.  ^     ^uct      Qf     a     pOison_gland     whose 

secretion  they  instil  into  the  insects  which  constitute 
their  prey.  The  stomach  is  like  a  hollow  ring  from 


Spiders.  1 1 1 

which  radiating  blind  pouches  pass  off,  and  the  diges- 
tive tube  is  short. 

Near  the  hinder  end  of  the  abdomen  in  spiders, 
there  is  a  flattish  '  spinning  area '  upon  which  open  the 
glands  which  secrete  the  web.  On  this  area  there  are 
usually  three  pairs  of  little  wart-like  spinnerets ;  and 
numerous  small  pores,  from  each  of  which  a  minute 
thread  of  web-material  issues,  open  on  the  surface  of 
each  spinneret.  Sometimes  one  pair  of  the  little  knobs 
consists  of  a  palp-like  process.  In  the  common 
house-spider  (Tegenaria  domestica)  there  are  400  such 
holes  on  each  wart,  hence  each  thread  of  the  web 
consists  of  several  hundred  strands ;  the  material  is  at 
first  fluid,  but  rapidly  becomes  hard  and  chitnoid. 
In  commencing  to  spin,  the  spider  applies  the  spin- 
nerets to  the  surface  of  some  fixed  body,  and  then  as 
it  moves  away,  the  material  is  drawn  out.  The  hind 
feet  press  the  several  strands  of  the  web-thread  to- 
gether, their  comb-like  claws  appearing  to  be  im- 
portant instruments  for  this  purpose. 

In  the  web  of  the  garden  spider,  whose  geometrical 
nets  are  frequently  seen  on  old  fences  and  palings, 
tli ere  are  three  kinds  of  threads  to  be  noticed,  ist 
The  marginal  and  stoutest  radial  threads.  2nd.  The 
intermediate  radial  threads,  both  of  which  are  uniform, 
though  differing  in  size  and  in  elasticity,  wherein  the 
secondary  exceed  the  primary.  3rd.  The  concentric 
threads  which  are  bedecked  at  regular  intervals  with 
little  viscid  globules. 

Other  spiders  excavate  cavities  in  the  ground ;  these 
they  line  with  a  silky  web,  and  over  the  mouth  of 
them  they  make  a  trap-door  lid  of  alternate  layers  of 


1 12  Invertebrata. 

earth  and  web  united  together  and  hinged  by  a  silken 
hinge.  These  trap-door  spiders  are  found  along  the 
shores  of  the  Mediterranean,  in  California  and  Ja- 
maica. Some  spin  little  cocoons  or  silken  cases  for 
their  eggs,  which  theycarry  about  with  them,  and  -in 
protecting  which  they  exhibit  great  activity.  The 
maxillary  palps  are  never  pincer-bearing  or  used  for 
walking,  although  sometimes  long. 

Scorpions. — The  scorpions  and  their  allies  are 
characterised  by  the  possession  of  a  long  segmented 
abdomen,  ending  in  a  tail-like  portion.  The  maxil- 
lary palps  form  pincers,  like  crabs'  claws,  and  breath- 
ing takes  place  by  pulmonary  sacs  like  those  of 
spiders.  The  last  joint  of  the  abdomen  bears  in 
scorpions  a  sharp  spine  at  its  end,  perforated  by  the 
duct  of  a  poison-gland,  and  thereby  it  inflicts  painful 
wounds.  A  little  creature  named  Chelifer,  some- 
what allied  to  scorpions,  but  with  no  tail  nor  sting,  is 
often  found  in  old  books. 


CHAPTER  XXI. 

CENTIPEDES.      GALLYWORMS. 

CLASS  III.  Myriopoda. — This  comparatively  small 
class  includes  the  centipedes,  whose  long  jointed  bodies 
are  to  be  seen  rapidly  crawling  under  old  rotten  sticks 
and  stones  and  shunning  the  light.  In  this  country 
they  rarely  exceed  three  inches  in  length,  but  in  the 
tropics  they  reach  from  six  to  twelve  inches  or  even 
more,  and  their  bites  are  poisonous  and  severe.  One 


Centipedes.  113 

British  form  is  phosphorescent,  and  another  is 
described  as  capable  of  giving  electric  shocks.  The 
body  consists  of  many  segments  which,  with 
the  exception  of  the  head  and  the  last  joint, 
are  similar  in  appearance  ;  the*  head  bears 
the  eyes,  which  are  usually  simple  like  those 
of  spiders,  and  generally  in  two  rows.  Near 
these  there  are  the  sensitive,  slender,  thread- 
like, antennae,  consisting  rarely  of  seven, 
usually  of  fourteen  joints  or  more.  These 
animals  are  usually  carnivorous  and  have  a 
strong  pair  of  mandibles,  situated  on  each 
side  of  the  mouth,  and  two  pairs  of  maxillae, 
either  or  both  of  which  are  sometimes  united 
together  in  the  middle  line,  forming  a  lower  e(/,SL-* 
lip  for  the  mouth ;  the  anterior  of  these  have  blu£)' 
jointed  palps.  The  hindermost  segment  of  the  body 
has  often  a  pair  of  long  limbs  directed  backwards. 
There  is  a  straight  digestive  canal  with  a  number  of 
tortuous  glands  appended  to  it,  .and  a  long  tubular 
heart  made  up  of  a  chain  of  chambers  one  in  each 
segment  separated  from  each  other  by  valves. 

On  each  side  of  the  body  open  the  mouths  of  the 
tracheae  or  tubes  for  breathing  ;  there  may  be  one  on 
each  segment  or  one  on  every  second  joint  Each 
opening  is  the  beginning  of  an  air-tube,  which  on 
entering  the  body  branches  irregularly,  the  fine 
branches  freely  communicating  with  each  other.  To 
keep  these  tubes  open  there  is  a  spirally  coiled  thread 
of  chitin  in  their  lining  membrane,  which  like  a  spring 
prevents  them  from  collapsing,  and  to  keep  the  mouth 
from  being  choked  there  is  usually  a  raised  margin 
I 


1 14  Invertebrata. 

sometimes  provided  with  little  processes.   One  curious 
group  has  no  tracheae. 

Many  of  these  centipedes  have  minute  pear-shaped 
glands  placed  along  the  sides,  which  secrete  a  brown 
irritating  fluid,  emitting  a  disagreeable  odour. 

There  are  more  than  twenty  segments  in  the  body 
(except  in  one  little  species),  and  each  bears  one  or 
two  pairs  of  legs,  all  with  six  or  seven  joints  like  those 
of  a  spider  or  crustacean ;  each  limb  terminates  in 
one  or  two  claws. 

Subdivisions. — There  are  three  orders  of  these 
animals,  millepedes,  centipedes,  and  pauropods. 
Millepedes  possess  two  pairs  of  limbs  on  most  of  their 
segments,  a  condition  due  to  the  union  of  the  true 
segments  in  pairs.  They  have  also  small  antennae 
of  seven  joints  and  tracheal  openings  in  front  of  the 
articulation  of  each  leg.  They  are  found  in  this  coun- 
try in  the  rotten  wood  of  decaying  trees,  and  when 
disturbed  roll  themselves  up  into  balls. 

Centipedes  are  found  under  stones  in  damp  out- 
houses, or  in  rotten  palings.     They  have  but  one  pair 
of  limbs  on  each  joint  of  the  body,  and  never  more 
than  one  pair  of  stigmata.     The  native  forms  are  small, 
but  the  tropical  Scolopendrae  are  of  very  large  size  and 
their  bites  are  exceedingly  severe.     The  one  species 
of  Pauropus   is   a   minute  white  creature  found  in 
decaying  leaves,  with  no  tracheae,  ten  segments  and 
five-jointed  antennae. 


Structure  of  an  Insect. 


CHAPTER  XXII. 

INSECTS. 

CLASS  IV.  Insecta. — Insects,  the  most  numerous  and 
the  most  highly  organised  of  invertebrates  are  found 

FIG.  62. 


Grasshopper,  showing  the  structure  and  composition  of  an  insect's  body. 
a,  head  ;  £,  eye ;  c,  antenna  ;  rf,  thorax,  foremost  segment ;  f,  foremost 
pair  of  legs  ;  _/i  middle  segment  of  thorax  ;  g,  foremost  pair  of  wings  ; 
A,  second  pair  of  legs  ;  /',  hindmost  segment  of  thorax  ;  /',  posterior  pair 
of  wings  ;  /4r,  femur  of  third  pair  of  legs  ;  /,  tibia  ;  m,  tarsus  ;  al>, 
abdomen. 

in  almost  every  conceivable  locality  on  the  earth's 

I   2 


1 1 6  Invertebrata. 

surface.  Scarcely  a  plant  exists  but  it  harbours  some 
one  of  the  tribe,  and  many  animals,  living  or  dead, 
supply  food  for  other  species.  Insects  are  usually  of 
small  size  and  have  the  six  foremost  segments  united 
to  form  a  head.  The  three  succeeding  segments  form 
a  thorav,  which  alone  bears  the  legs,  one  pair  on  each 
of  its  rings,  and  when  wings  are  present  they  are  borne 
by  the  middle  and  hindmost  of  these  thoracic  rings. 
The  abdomen  consists  of  seven  segments  not  bearing 
any  limbs,  and  followed  by  one,  two  or  three  abdom- 
inal rings,  to  which  are  appended  the  sting  or  its 
equivalent,  the  ovipositor.  A  black  beetle,  a  blue- 
bottle fly,  and  a  butterfly  may  be  taken  as  types  of 
the  class. 

Organs  of  Sense. — The  head  of  an  insect  bears  a 
pair  of  compound  eyes,  and  often  several  simple  eyes 
in  a  cluster.  The  former  have  a  cornea  or  transparent 
surface  divided  into  many  facets,  each  of  the  nerve  rods 
having  its  own  pigment  mass  and  its  own  cornea. 
In  the  common  house-fly  there  are  2000  such  facets 
in  each  eye,  and  in  the  dragon-fly  there  are  28,000. 

The  head  of  an  insect  also  bears  one  pair  of 
antennce  or  feelers,  jointed  organs  which  vary  much  in 
shape  and  structure,  being  sometimes  simple,  filiform, 
comb-like,  or  lamellar.  These  are  organs  of  touch 
and  hearing,  possibly  of  smell  and  taste,  and  also  of 
communication  between  one  insect  and  its  fellow. 

Month. — The  mouth  is  on  the  fore  and  under  part 
of  the  head  and  varies  in  shape  according  to  the 
method  whereby  the  insect  obtains  its  food.  In  beet- 
les, dragon-flies,  &c.,  the  mouth  is  armed  with  chew- 
ing jaws.  There  are  two  lips,  an  upper  or  iabrum  (fig. 


Mouths  of  Insects. 


117 


65,  e)  and  lower  or  labium.     The  lower  (/)  represents 

the  second  pair  of  max- 

illae  in  the   lobster  and 

crayfish,  which  here  are 

united      together,      but 

sometimes   as    in   cock- 

roaches    (fig.    64)    and 

locusts   remaining  sepa- 

rate. The  labium  bears  a 

pair  of  feelers  called  labial 

palps  (k).     Between  the 

and    the    labium    Under  side  of  mouth  of  Cockroach. 


f     .  maxillary     palp  ;    i,   ligula ;  *  para- 

are     tWO     pairs      Of     ja\VS        gloss* ;  k,   labial  palp ;  i,   cardo   of 

placed  vertically,  so  that 


FIG.  65. 


hinge  ;  2.  stipes  ;  5,  maxilla  ;  6,  galea, 
or  sensitive  process  of  maxilla. 

FIG.  66. 


Upper  side  of  head  of  Cockroach. 

I,  epicranium,  or  top  of  the  head  ;  d,  clypeus; 

e,  labrum  ;  f,  mandibles  :  A,  antennae. 


Mouth  of  Flea. 
Showing  the  slender  style- 
like  labrum  between  the 
long  mandibles  medially, 
and  the  labial  and  max. 
illary  palps  laterally. 


in  acting  they  move  in  a  horizontal  plane.     The  uppei 


1 1 8  Invertebrata. 

pair  are  named  mandibles  or  biting  jaws,  the  lower  pair 
maxillae  or  chewing  jaws.  The  last-named  have  usually 
appended  to  them  on  each  side  a  pair  of  small 
jointed  feelers  or  maxillary  palps.  In  the  bluebottle 
and  house-fly  the  lower  lip  is  lengthened  into  an  elon- 
gated gutter-like  sheath  in  which  are  contained  the 
maxillae  and  mandibles,  which  are  reduced  to  mere 
bristle-like  processes. 

In  the  bee  (fig.    77,  p.   132)  the  upper  lip  and 
mandible   are  strong  and  fitted   for  chewing,  while 
FIG.  67.  tne  rnaxillae  and  lower  lip  are  long 

and  channelled,  so  that  when 
placed  in  apposition  they  make 
a  tube  through  which  the  insect 
sucks  in  honey.  In  these  crea- 
tures the  lower  lip  consists  of 
two  parts,  an  upper  or  tongue 
and  a  hinder  part  or  mentum. 
In  the  butterfly,  the  mouth  has 
lost  all  trace  of  its  chewing  func- 
tion and  the  maxillae  form  two 
half  tubes,  and  when  opposed  as 

Head  and  proboscis  of  But-     ,  .  .  , 

terfly,  showing  antennae  they  always  are  they  make  up  a 
canal,  and  being  very  long  and 
curved,  this  is  sometimes  called  the  proboscis.  Each 
of  these  maxillae  has  within  it  also  a  fine  tube,  and  thus 
a  transverse  section  through  the  proboscis  shows  three 
tubes,  one  medial  between  the  maxillae  and  one  lateral 
on  each  side  within  each  maxilla.  Behind  this  proboscis 
lies  the  labium,  which  has  usually  large  palps  between 
which  the  proboscis  lies  when  retracted  ;  for,  unlike 
the  tube  in  the  bee,  this  proboscis  is  freely  retractile. 


Nervous  System  of  Insects.  119 

Body. — The  head  is  joined  to  the  thorax  by  a  nar- 
row neck,  and  this  region  is  generally  strong,  and  the 
limbs  are  attached  to  the  under  part  of  the  side  of 
each  of  its  three  rings.  Each  limb  is  composed  of 
five  joints  :  hip  (coxa ),  a  ring  segment  (trochanter),  thigh 
(femur,  fig.  63,  k],  a  shin  (tibia],  and  a  tarsus  of  seve- 
ral joints  ending  in  the  claws  to  which  sucking  cushions 
or  pads  may  be  appended.  The  wings  are  jointed  to 
the  middle  and  hinder  rings  of  the  thorax ;  these  are 
modified  lateral  flaps  of  the  body  wall,  such  as  exist  in 
some  crustaceans ;  the  thin  skin  folds  of  which  they 
consist  are  supported  by  chitinous  ribs  (costa)  con- 
taining branches  of  the  tracheae. 

Internal  Structure. — On  the  sides  of  each  abdo- 
minal ring  are  the  apertures  of  the  long,  finely  branch- 
ing tracheae,  which  sink  into  the  body  and  are  distri- 
buted widely  among  the  tissues.  Each  tube  has  a 
membranous  wall  strengthened  by  a  coiled  spiral 
chitinous  thread  which  keeps  it  open  for  conveying 
air  from  the  surface  through  the  body.  Each  motion 
of  the  body  by  altering  the  tension  of  the  vessels  pro- 
motes this  method  of  respiration.  The  dorsal  tubular 
heart  placed  in  the  abdomen,  consists  of  a  chain  of 
chambers  separated  the  one  from  the  other  by  valves. 
This  receives  the  impure  blood  and  the  new  blood 
from  the  intestines,  and  propels  it  by  the  chief  blood- 
vessels into  lacunae  or  interspaces  between  the  tissues 
which  are  thus  nourished.  The  blood  is  colourless, 
or  green,  rarely  red. 

Insects  have  two  large  and  complex  nerve  ganglia 
in  the  head,  and  ganglia  in  all  the  segments  from  the 
head  backwards.  The  head  ganglia  send  branches 


120 


Itivertebrata. 


to  the  eyes  and  appendages,  while  the  thoracic  ganglia 
supply  the  limbs.  Some  cave-dwelling  insects  have 
no  eyes,  others  have  these  organs  rudimental.  The 
digestive  canal  of  insects  consists  of  a  stomach  to 
FIG.  es.  which  the  long  oesophagus  or 

gullet  leads  from  the  mouth ; 
to  this  a  thin  walled  sac  or 
sucking  stomach  may  be  ap- 
pended as  in  butterflies,  in 
others  there  is  a  gizzard  with 
hard  horny  tooth-like  pro- 
cesses, and  this  is  followed 
by  the  glandular  thin- walled 
true  digestive  stomach  which 
ends  in  an  intestine,  whose 
length  depends  on  the  nature 
of  the  food,  being  longer  in 

Nervous    system    of    Beetle,  °  f 

showing  central  double  nerve   thOSC  that   feed    On    SOlld    than 
cord  and  chain  of  ganglia. 


matter,  and  longer  in  the  herbivorous  than  in  the 
predaceous  forms.  Glandular  tubes  opening  into 
the  end  of  the  intestine  exist  in  many  insects,  and 
from  their  first  describer  are  known  as  Malpighian. 

Some  insects  are  luminous.     In  the  glow-worm 
(Lampyris  noctilucd]  there  is  a  large  fatty  body  in 
FIG.  69.  the   abdomen  richly  supplied  with 

tracheae  and  nerves  from  which  a 
bright  light  is  emitted.  The  fire-fly 
(Elater  noctilucus)  sends  out  light 
from  two  oval  spots  on  the  thorax. 
Grasshoppers  and  crickets  emit 
sounds  by  rubbing  one  part  of  the 


Metamorphoses  of  Insects.  121 

body  against  another,  and  such  have  usually  a  special 
hearing  organ  which  in  crickets  and  locusts  is  placed 
under  the  knee  on  the  outside  of  the  foremost  pair  of 
limbs. 

Development  and  Metamorphoses. — Insects'  eggs 
have  often  a  sculptured  shell,  and  are  laid  in  such 
places  as  are  suitable  for  the  supply  of  food  to  the 
newly  hatched  larvae.  For  this  egg-laying  the  parent 
has  often  an  organ  formed  of  the  modified  append- 
ages of  the  abdomen.  These  organs  are  in  the  form 
of  bristles,  pincers,  or  saws,  and  by  these  the  insect 
prepares  the  place  for  and  deposits  its  eggs ;  hence, 
the  organ  is  called  an  ovipositor. 

The  young  of  most  insects  emerge  from  the  eggs 
as  worm-like  animals  called  caterpillars  or  larvae. 
These  are  little  jointed  creatures,  having  a  head  which 
bears  eyes  and  a  pair  of  antennae.  Its  mouth  is  armed 
with  strong  jaws,  and  the  surface  is  often  covered  with 
bristles.  Each  of  the  three  anterior  segments  of  the 
body  of  a  caterpillar  is  usually  provided  with  a  pair  of 
little  stumpy  feet,  and  sometimes,  as  in  the  larvae  of 
butterflies,  flies  and  saw-flies,  the  hinder  joints  have 
also  foot- like  processes.  Caterpillars  are  most  voraci- 
ous in  their  habits  and  grow  rapidly,  frequently  moult- 
ing or  shedding  their  skin.  On  reaching  the  limit  of 
size,  many  caterpillars  begin  to  spin  for  themselves  a 
case  or  cocoon.  The  glands  from  which  this  pro- 
ceeds are  two  long  tubes  placed  behind  the  head,  but 
opening  on  the  lip,  and  the  material  of  the  cocoon 
is  silk.  When  caterpillars  are  fully  fed  they  give 
up  eating,  and  their  skin  thickening  they  become 
fixed  and  rigid  and  are  known  as  pupae,  or  from 


1 22  Invertebrata. 

their  occasional  metallic  lustre,  chrysalides.  In  this 
pupa  stage  the  animal  lies  for  a  considerable  time; 
this  skin  then  bursts  and  the  perfect  insect  emerges, 
at  first  soft  and  moist  but  soon  becoming  firm  and 
fit  for  independent  life. 

Caterpillars  differ  much  in  structure  from  the 
adult  insect;  thus  the  digestive  canal  of  the  cater- 
pillars of  butterflies  is  fitted  for  the  digestion  of 
solid  food,  while  that  of  the  imago  or  perfect  insect 
is  only  fitted  for  sucking  the  juices  of  plants.  The 
antennae  likewise  of  caterpillars  are  attached  to  the 
front  edge  of  the  forehead  shield,  and  outside  the 
articulation  of  the  mandible,  whereas  the  antennae 
of  the  imago  or  perfect  insect  is  articulated  further 
forward,  and  on  a  plane  with  the  joint  at  the  base 
of  the  mandible ;  thus  the  antennae  of  the  caterpillar 
represent  the  long  antennae  of  the  crab  and  lobster, 
while  those  of  the  perfect  insect  represent  the  anten- 
nule  of  crustaceans.  Insects  display  an  amount  of 
intelligence  far  superior  to  that  of  the  lower  verte- 
brates; ants,  wasps,  and  bees,  the  most  highly  or- 
ganised as  well  as  the  most  intelligent  of  the  class, 
exhibit  a  wonderful  power  in  the  mode  of  ordering 
and  governing  their  communities,  and  the  skill  shown 
in  the  construction  of  their  habitations  is  scarcely 
inferior  to  that  of  man  himself. 

There  are  at  least  thirteen  orders  of  insects  known 
to  the  naturalist,  a  few  of  the  commoner  and  more 
interesting  representatives  of  which  are  shortly  de- 
scribed in  the  next  two  chapters. 


Bugs.     Spring  tails.     Eat  wigs.          123 
CHAPTER  XXIII. 

ORDERS   OF    INSECTS. 

ORDER  I.  Bhynchota.— This  group  consists  of 
those  insects  which  either  undergo  no  metamorphoses 
or  a  very  slight  change  in  FIG.  70. 

the  process  of  growth. 
They  have  almost  all 
suctorial  mouths  (fig.  70), 
consisting  of  a  long  tubu- 
lar labium,  whose  base  is 
open  or  covered  by  the 
labrum  like  a  little  lid. 
The  mandibles  and 
maxillae  are  altered  into 
piercers  or  bristles  which 
work  within  the  tube.  A 
few,  however,  like  the 
bird-lice,  have  hook-like 
mandibles  and  chewing 

mOUths.  Many  Of  the  Showing  the  median  elongated  labium, 
incf^tc  r\f  tVn'c  rvrrl^r  arp»  tne  f°ur  bristle-like  mandibles  and 

insects  ot  this  order  are     maxillaet  also,  at  ^  sideSj  Ac  an_ 
parasites    and     wingless,     tennae  and  «*«• 
such  as  lice  and  bugs ;  others,  the  aphides,  the  small 
green  insects  which  are  so  abundant  on  roses,  gera- 
niums, &c.,  are  plant  parasites. 

These  aphides  are  marvellously  prolific,  a  single 
pair  being  capable  in  one  year  of  producing  a  progeny 
of  twenty  thousand  millions  or  even  more.  Some 
aphides  have  glandular  tubes  on  the  abdomen  which 
secrete  a  sweet  honey-like  fluid.  This  fluid  is  used 


124  Invertebrata. 

as  food  by  some  species  of  ants,  especially  in  this 
country  by  the  red  and  yellow  ants,  which  can  be 
seen  to  'milk'  the  honey  tubes  with  their  antennae 
and  swallow  the  fluid.  Several  species  of  aphides 
appear  to  be  kept  as  '  milch  kine '  by  these  ants,  and 
are  fed  by  them  apparently  for  this  secretion. 

Other  representatives  of  this  order  are  the 
cochineal  and  lac  insects,  the  *  water  boatmen 'and 
'  water  scorpions/  as  well  as  the  numerous  and  often 
brightly  coloured  field  bugs. 

ORDER  II.  Thysanura. — Spring- tails,  an  unim- 
portant group,  consisting  mostly  of  very  small  crea- 
tures, sugar-lice  and  spring-tails,  which  live  in  dark, 
damp  cellars,  or  in  sugar  stores,  and  can  be  seen 
hopping  or  springing  about  and  shunning  the  light. 

They  scarcely  undergo  metamorphoses,  and  their 
mouths  are  suited  for  chewing.  The  extremity  of  the 
abdomen  is  prolonged  into  a  pair  of  bristles  or  a 
forked  tail,  whereby  the  animal  is  enabled  to  progress 
by  leaping.  The  scales  of  the  bodies  of  some  of 
these  Podurae  or  spring-tails  are  marked  with  very 
minute  furrows. 

ORDER  III.  Euplexoptera. — This  order  includes 
the  earwigs,  which  are  remarkable  for  their  curiously 
folded  hind  wings,  that  lie  folded  like  a  fan  under 
cover  of  the  hard-shielded  forewings.  They  have  a 
masticating  mouth,  and  posteriorly  there  is  a  pincer- 
like  long  abdominal  appendage  in  both  male  and 
female.  The  earwig  is  remarkable  for  sitting  on  her 
eggs  to  hatch  them,  and  for  the  maternal  protection 
which  the  female  exercises  over  her  young  which 
resemble  her  except  in  the  absence  of  wings. 


p-r 

Thrips.     Cockroaches.     Locusts.          12$ 

ORDER  IV. — Thysanoptera,  or  fringe-winged  in- 
sects, including  a  not  uncommon  little  fly,  named 
Thrips,  whose  contact  with  the  face  in  warm  weather  is 
often  a  source  of  considerable  itching  from  the  titilla- 
tion  caused  by  its  plumose  wings  and  bristled  body. 
One  species  of  this  order  by  piercing  the  immature  wheat 
grain  with  its  bristle-like  mandibles  causes  the  seed  to 
shrivel,  and  occasionally  destroys  even  the  corn  stalks. 

ORDER  V. — Orthoptera,  straight-winged  insects, 
includes  cockroaches,  grasshoppers  and  locusts. 
These  have  four  wings,  of  which  the  often  parchment- 
like  front  pair  are  the  smaller ;  the  second  pair  are 
usually  large,  and  when  at  rest  are  folded  like  a  fan. 
The  mouth  is  masticatory  and  both  pairs  of  maxillae 
are  free.  Some  of  the  tropical  forms  of  this  order 
are  wingless  and  assume  extraordinary  forms,  the 
walking  leaves,  mantis,  and  walking  stick  (Bacterium) 
sometimes  resembling  dry  twigs  or  bits  of  branches. 
In  the  common  cockroach  (Periplaneta  orieiitalis) 
which  is  a  native  of  the  East,  the  legs  are  fitted  for 
running  and  have  spiny  tibiae,  the  head  is  over- 
lapped by  the  front  segments  of  the  thorax  and 
bears  long  antennae,  and  the  parts  of  the  mouth  are 
distinct  (figs.  64,  65).  The  wings  are  very  small, 
especially  in  the  females.  The  Drummer  Cockroach 
of  the  West  Indies  adds  to  its  other  disagreeable 
qualities  that  of  making  a  knocking  noise,  which  is 
sometimes  sufficiently  loud  to  keep  awake  the  inhabi- 
tants of  houses  infested  with  these  insects.  Troctes 
pulsatorius,  a  minute  insect  found  in  books,  old  pic- 
tures, &c,  also  produces  a  sound  which  has  earned  for 
it  the  name  '  death-watch ;  or  '  death-tick.' 


126  Invertebrata. 

Locusts  are  terrible  scourges  in  tropical  countries, 
devouring  all  vegetation  and  leaving  bare  the  regions 
over  which  they  pass.  Their  body  is  long  and 
laterally  compressed  and  the  long  hind  legs  act  as 
leaping  organs.  They  produce  a  chirping  sound  by 
rubbing  the  thighs  against  the  elevated  ribs  of  their 
wings.  In  the  grasshopper  and  cricket  a  similar 
sound  is  produced  by  the  rubbing  together  of  spots  on 
the  wings  provided  with  raised  ridges. 

The  white  ants  or  Termites  of  tropical  regions 
also  belong  to  this  order,  and  build  ant-hills  of  extra- 
ordinary size  and  hardness.  Their  colonies  are  very 
complex,  and  consist  of  several  kinds  of  inhabitants, 
females,  males,  workers  and  soldiers. 

The  dragonflies,  which  also  belong  to  this  order, 
have  aquatic  larvae,  breathing  by  means  of  tracheal 

FIG.  71. 


Larva  of  Dragonfly,  showing  the  '  Mask.' 

gills  or  tuft-like  processes  of  their  body- wall  contain- 
ing tracheae,  but  with  no  openings.  These  processes 
are  lost  in  the  perfect  insect ;  in  one  American  genus, 
however,  these  appendages  are  retained  during  life. 
The  larva  of  the  common  dragon-fly  has  a  long  and 
jointed  under  lip,  which  is  folded  over  the  face  when 
at  rest  and  is  called  the  mask,  but  when  the  animal  is 
feeding  it  becomes  extended  as  a  formidable  tongs- 
like  weapon  for  the  grasping  of  prey  (tig.  71). 


Fleas.    Flies.  127 


CHAPTER  XXIV. 

INSECTS  WHICH  UNDERGO  PERFECT  METAMORPHOSES. 

THE  four  orders  of  insects  which  follow  are  small, 
but  contain  some  interesting  forms  which  deserve  a 
passing  notice.  FlG  ?2 

ORDER  VI.      Neuroptera, 
nerve-winged  insects,  including 
the  scorpion-flies  (fig.  7  2  ^snake- 
flies,    and  ant-lions.     These  in 
their  perfect    stage  possess    a 
mouth  fitted   for  chewing,  and 
four  equal  membranous  wings,      Pan°n».  or  Scorpion-fly, 
of  which  the  hinder  pair  are  never  folded.     Few  of 
these  insects  are  natives  of  this  country. 

ORDER  VII. — Trichoptera,  including  the  caddis- 
flies  which  have  hair-clad  or  scaly  unequal  wings,  the 
hinder  of  which  are  folded.  Their  larvae  agglutinate 
small  shells,  stones,  straws  &c.  by  silken  threads 
secreted  by  a  small  spinning  gland  placed  on  the 
lower  lip,  and  of  these  they  make  cases  in  which  they 
live.  Having  attained  its  full  size,  the  pupa  fixes  its 
case  under  water  and  spins  a  silken  network  or  grating 
over  each  end  of  it,  thus  shutting  itself  in  for  its  pupa 
sleep,  while  it  does  not  exclude  the  water  which  it 
requires  for  breathing.  After  this  stage  of  rest  the 
pupa  by  its  strong  jaws  bites  through  its  prison,  and 
after  moulting  assumes  its  adult  form. 

ORDER  VIII. — Strepsiptera  includes  the  curious 


128  Invertebrata. 

parasites  which  live  on  the  abdomen  of  bees  and 
wasps.  In  these  the  males  have  four  wings,  two  in  front, 
small  and  twisted,  from  which  the  order  is  named, 
two  behind,  large  and  fan-like  ;  the  females  never  lose 
their  last  pupa-skin,  and  are  wingless,  with  a  worm-like 
abdomen  and  are  viviparous. 

ORDER  IX.  Aphaniptera. — Includes  fleas  which 
have  laterally  compressed  bodies  and  exceedingly 
rudimental  wings,  the  scale-like  traces  of  which  are 
with  difficulty  noticeable.  The  suctorial  mouth  (fig. 
66),  without  upper  lip,  has  long  slender  saw-like 
mandibles,  which  are  sheathed  by  the  three-jointed 
labial  palps  at  their  base. 

The  antennae  are  very  small  and  lie  in  a  groove, 
but  the  maxillary  palps  are  large  and  prominent.  The 
hindmost  pair  of  limbs  are  long,  muscular,  and  well- 
fitted  for  leaping.  The  larvae  are  white  footless  grubs 
which  feed  on  animal  matter  for  about  twelve  days,  spin 
for  themselves  a  cocoon,  and  pass  to  the  pupa  stage. 
After  about  fourteen  days'  quiescence  in  this  stage  the 
perfect  insect  emerges.  In  many  respects  the  flea  is 
closely  allied  to  the  next  order. 

ORDER  X. — Diptera,  two  winged  flies,  including 
flies,  gnats,  mosquitoes,  &c.  In  this  order  the  hind 
pair  of  wings  is  rudimental  and  represented  by  scale- 
like  or  pin-like  processes  under  the  developed  pair  of 
wings,  and  the  mouth  is  a  proboscis.  The  larvae  are 
footless,  often  headless  maggots,  such  as  are  found  on 
putrid  meat.  Some  forms  of  Diptera,  like  the  gnats 
and  mosquitoes,  are  provided  each  with  a  long  pro- 
boscis enclosing  six  long  sharp  bristles.  The  larvae  of 
the  gnats  are  aquatic  and  breathe  air  by  means  of  a 


Moths.  129 

tube  with  which  they  are  provided  which  opens  at  the 
surface  of  the  water.  Some  of  these  insects  are  very 
destructive  to  vegetation ;  the  larvae  of  the  common 
daddy-longlegs  for  instance,  feeds  on  the  roots  of  grass 
and  will  thus  sometimes  destroy  large  patches  of 
meadow.  The  Hessian  fly  is  still  more  formidable, 
often  destroying  whole  fields  of  wheat  by  attacking 
the  young  plants  before  they  are  in  flower. 

ORDER  XI. — Lepidoptera,  is  also  a  large  order, 
and  includes  those  most  beautiful  of  all  insects,  the  but- 
terflies, characterised  by  possessing  four  wings  covered 
with  fine  dust-like  scales.  These  microscopic  scales 
overlap  each  other  on  the  surface  of  the  wings,  and  are 
of  different  shapes  in  different  species.  Butterflies  have 
suctorial  mouths  (fig.  67),  the  proboscis-like  sucker 
being  rolled  up  when  not  in  use.  The  larvas  or  cater- 
pillars consist  of  thirteen  joints  and  are  very  unlike  in 
mouth,  structure,  and  general  appearance  to  the  perfect 
forms  which  emerge  from  them. 

On  the  lower  lip  in  the  larvae  of  some  moths  there 
is  the  outlet  of  two  spinning  glands,  which  when  the 
larva  has  reached  its  full  size  secrete  the  material  for 
a  silken  cocoon  within  which  it  is  enclosed  in  the  pupa 
state. 

These  insects  vary  in  size ;  some,  as  the  clothes 
moths  and  fur  moths,  are  very  small. 

The  larvae  of  the  leaf-rollers,  a  form  nearly  allied 
to  the  clothes-moth,  roll  up  the  leaves  of  plants  on 
which  they  feed  into  tubes,  within  which  they  live  and 
pass  their  pupa  sleep,  and  whence  they  emerge  in 
due  time  as  little  broad-winged  moths. 

Another  related  form  often  found  on  apple  trees  is 


130 


Invertebrata. 


the  looper  or  canker-worm  moth,  named  from  the  pecu- 
liar looped  attitude  which  the  larva  assumes  in  walking. 
The  silkworm  moth,  a  native  of  North  China,  secretes 
by  its  two  glands  the  silk  of  commerce.  The  sphinx 
moths,  called  so  from  the  attitude  in  which  the  cater- 


FlG.   73- 


FIG.  74- 


Chrysalis. 


Deilephila  Elpenor,  Hawk  Moth. 


pillars  are  often  found,  with  their  heads  and  fore  parts 
raised,  are  known  by  their  prismatic  antenna?  and  by 
the  long  horn  on  the  tail  end  of  the  caterpillar.  One 
of  these,  the  tomato  or  tobacco  sphinx  moth  (whose 
large  green  larva  feeds  on  leaves  of  those  plants)  bears 
on  each  side  of  its  abdomen  five  large  yellow  patches. 

While  nearly  all  moths  are  nocturnal,  the  true 
butterflies,  recognised  by  their  brighter  colours  and 
their  club-shaped  antennae,  are  diurnal  in  their  habits. 

The  best  known  examples  are  the  white  cabbage 
butterfly,  the  nettle  tortoiseshell,  and  the  thistle  painted 


Beetles.  131 

lady  butterflies.     The  larvae  of  the  true  butterflies  do 
not  spin  a  cocoon. 

ORDER  XII.  Coleoptera. — Beetles  form  numeri- 
cally the  largest  sub-division  of  the  animal  kingdom, 
there  being  over  seventy  thou-  FIG.  75. 

sand  species.  In  these  the  fore 
wings  are  converted  into  a  hard 
thick  pair  of  wing-covers  or  elytra 
overlapping  the  hinder  pair,  which 
are  membranous,  folded,  and 
usually  capable  of  flight.  Beetles 
are  found  in  almost  every  condition 
and  feed  on  almost  every  kind 
of  material ;  cayenne  pepper,  can- 
tharides,  medicinal  rhubarb,  animal  and  Pu?a- 
effete  matter,  putrid  flesh  and  decaying  vegetables  are 
the  favourite  nourishment  of  some  forms. 

There  are  forty-eight  families  included  in  this 
*  polymorphic  '  order  ;  one  of  these  contains  the  little 
ladybird  or  Coctinella,  whose  spotted  bodies  are  often 
seen  on  nettles  in  pursuit  of  the  aphides  on  which  they 
feed.  It  has  only  three  large  joints  in  the  tarsus  of 
each  foot.  The  destructive  Colorado  or  potato  beetle 
(Doryphora)  somewhat  resembles  the  ladybird  but  is 
ten-striped  and  not  spotted.  Many  beetles  are  ex- 
tremely destructive  to  vegetation,  both  in  their  larval 
and  perfect  states,  the  strong  mandibulate  mouths 
being  able  to  cut  even  hard  woods.  Of  these,  the 
turnip-fly,  the  wire-worm  (which  is  the  larva  of  the 
beetle  called  Agriotes),  the  pine-beetle,  the  typographic 
beetle,  Scolytus  the  elm-beetle,  Lymexylon  the  oak- 
beetle,  are  illustrations. 

KJ 


132  Invert  cbrata. 

Other  beetles  are  found  in  articles  of  food,  such  as 
Tenebrio,  the  meal-worm  often  found  in  ships'  biscuits, 
FlG  ?6  Dermestes,    or    the    bacon 

grub;  others  are  the  pests 
of  museums,  like  the  little 
Anthrenus  or  Ptinus  the 
herbarium  beetle,  and 

The  blistering  \*<X\e(Canthans       PtiUmiS,    the       bookworm. 
vesicatoria).  ^   few  afe  temporary  para. 

sites;  thus  the  larva  of  Rhipidius  lives  in  the  abdomen 
of  the  cockroach.  Some  beetles  are  luminous,  such 
as  the  glowworm  and  the  firefly. 

Some  beetles  emit  an  ammoniacal  smell  when  irri- 
tated ;  others,  like  Meloe,  secrete  a  drop  of  acrid  oil 
under  the  same  circumstances.  This  secretion  renders 
the  bodies  of  some  of  them  useful  in  medicine  for 
blistering  purposes ;  thus  the  bodies  of  Cantharis  vesi- 
catoria  (fig.  76)  are  the  Spanish  or  blistering  flies  of 
commerce.  Some  species  of  beetles  inhabit  caves 
and  are  eyeless;  others  are  aquatic  and  fitted  for 
swimming.  The  sizes  of  beetles  are  also  exceedingly 
variable  ;  some,  like  the  large  Hercules  beetle,  being 
nearly  six  inches  long,  while  others  are  of  microscopic 
dimension.  The  antennae  are  of  very  variable  shapes 
and  sizes,  being  in  some  much  longer  than  the  body, 
in  others  very  short  and  inconspicuous  ;  in  some,  like 
the  common  cockchafer,  lamellar,  in  others  stag-horn- 
shaped,  &c. 

ORDER  XIII.— Hymenoptera  (membrane-winged) 
includes  bees,  wasps  and  ants,  and  in  these  the  com- 
plexity and  intelligence  of  the  class  culminates.  They 
are  characterised  by  having  four  naked  membranous 


Bees.      Wasps. 


133 


wings,  with  few  veins,  and  a  mouth  with  strong  man- 
dibles but  with  suctorial  labium  and  maxillae.  The 
abdomen  is  often  joined  to  the  thorax  by  a  narrow 
foot-stalk  and  the  abdominal  tip  is  modified  into 
a  sting  which  consists  of  two  poison  glands  opening 

FIG.  77. 


i.  Mouth  of  the  Bee.  d,  clypeus  ;  e,  labrum  ;f,  mandible  ;g,  h,  maxilla  and 
its  palp  ;  *,  lingua  ;  **,  paraglossae.     2.  Tongue,  more  highly  magnified. 

into  a  common  vesicle  whose  duct  is  elongated  into 
a  tube  provided  with  a  piercer  barbed  at  the  point. 

In  bees  the  wings  are  not  folded  and  the  basal 
joint  of  the  hindermost  tarsus  is  flattened  and  often 
bristle-clad  to  collect  the  pollen  for  the  food  of  larvae; 


1 34  Invertebrata. 

hereby  many  of  them  lay  the  vegetable  kingdom 
under  great  obligation,  as  they  convey  the  pollen  from 
flower  to  flower  and  thereby  fertilise  the  seeds  of 
many  plants.  Many  bees  secrete  wax  by  means  of  a 
wax  gland  placed  in  the  abdomen,  and  with  this 
material  they  build  their  hexagonal  cells  for  the  shelter 
of  their  eggs  and  larvae. 

The  common  humble  bee  makes  a  nest  of  moss; 
others  use  clay  or  wood  ;  and  some,  like  cuckoos,  lay 
their  eggs  in  the  nests  of  other  species. 

In  the  hives  of  the  common  honey  bee  the  inha- 
bitants are  of  three  kinds,  the  queen  or  perfect  female, 
the  drones  or  males,  and  the  workers  or  imperfect 
females. 

Wasps  have  no  special  organ  for  the  collection  of 
the  pollen,  and  have  their  wings  longitudinally  folded; 
they  also  have  a  more  slender  petiole  or  stalk  joining 
the  abdomen  and  thorax.  Many  of  these  also  live  in 
colonies,  making  nests  of  paper  formed  of  vegetable 
matter  chewed  by  their  jaws  into  a  pulp  and  moulded 
into  hexagonal  cells  with  rounded  bases.  Other 
examples  are  the  saw-flies  which  have  a  saw-like  organ 
for  the  deposition  of  their  eggs,  and  the  Ichneumons, 
•which  have  the  singular  instinct  of  laying  their  eggs  in 
the  bodies  of  the  larvae  of  other  insects,  so  that  the 
young  are  hatched  in  the  midst  of  abundant  food,  for 
they  feast  upon  the  tissues  of  their  host  and  barely 
leave  him  enough  of  organ  to  prolong  existence  until 
they  are  ready  for  emergence. 

Other  Hymenopteious  insects  lay  their  eggs  under 
the  cuticle  of  plants;  and  thereby  form  small  tumours 
or  galls.  One  such  species  infests  the  oak  and  pro- 


Recapitulation.  1 3  5 

duces  the  nut-galls  so  important  in  the  manufacture 
of  ink.  Another  species  attacks  the  rose,  and  a  sin- 
gular gall-fly  has  a  cuckoo-like  habit  of  laying  its 
eggs  in  the  galls  formed  by  other  insects. 

The  ants  are  probably  the  most  intelligent  of  insects, 
having  the  most  complex  social  organisation  and  pos- 
sessing the  most  complex  nervous  system  in  proportion 
to  their  size  of  any  invertebrate.  The  males  and 
females  are  winged,  the  workers  are  wingless,  and  their 
sting  gland  secretes  formic  acid,  the  material  whereby 
they  irritate  or  sting.  No  group  of  animals  are  better 
worthy  of  study,  and  their  house-building  and  polity, 
slave-holding,  aphis-cow-keeping,  and  other  habits 
have  long  been  favourite  subjects  of  observation  with 
entomologists. 

The  ants  form  a  fitting  termination  to  the  Inverte- 
brata,  as  in  intelligence  and  in  interest  they  may  be 
looked  on  as  bearing  to  the  other  invertebrates  some- 
thing of  the  relation  which  man  has  to  his  neighbour- 
ing vertebrates. 

Becapitulation.— The  sub-divisions  of  insects  are 
by  some  looked  upon  as  deserving  of  a  higher  than 
ordinal  rank,  but  as  the  nature  of  a  group  depends  on 
the  nature  of  the  range  of  organic  structure  in  the  forms 
comprehended  therein,  and  not  on  the  number  of  in- 
cluded individuals,  we  cannot  but  see  that,  in  each 
order  of  insects,  the  component  species  are  constructed 
so  much  on  one  type  as  to  forbid  us  from  making  of 
them  more  than  ordinal  groups. 

The   orders   of   insects  which   we    have    briefly 
noticed  may  be  summarised  as  follows  : 
A.  Insects  with  imperfect  or  no  metamorphoses. 


136  Invertebrata. 

a.  With  suctorial  mouths,  wings  absent,  or 

when    present    having    the   fore  pair 
thickened.    Order  Rhynchota. 
Wings  four  equal,  membranous.     Order 
Thysanoptera. 

b.  With  masticatory  mouths,  abdomen  with 

a  terminal  appendix  of  bristles  or   a 

bifid  tail.     No  wings.      Order  Thy- 

sanura. 
Abdomen  with    a   terminal   two-bladed 

forceps.     Order  Euplexoptera. 
Abdomen  with  no  appendages,  wings  with 

reticulated  costse.     Order  Orthoptera. 
B.  Insects  which  pass  through  a  quiescent  pupa  stage. 
a.  Mouth  masticatory,  wings  membranous, 

equal.     Order  Neuroptera, 
Wings     hair-clad      or    scaly,     unequal. 

Order  Trichoptera. 

Fore-wings  converted   into  hard   wing- 
covers.     Order  Coleoptera. 
A  Mouth  suctorial,  with  rudi  mental  wings 

and  compressed  bodies.  Order  Aphan- 

iptera. 

With  two  wings.     Order  Diptera. 
With    four    wings,    the    anterior    short, 

twisted.     Order  Strepsiptera. 
Wings  large  and  scale-covered.     Order 

Lepidoptera. 
Wings  naked,  membranous,  few-veined. 

Order  Hymenoptera. 


INDEX    AND    GLOSSARY. 


ABD 

A  BDOMEN,    the  group  of  seg- 

*»  ments  of  the  body  which  con- 
tains the  digestive  organs. 

Aboral,  the  extremity  opposite  to  the 
mouth. 

Acamarchis,  a  moss-polype,  75 

Acamhocephala,  66 

Acarus,  a  mite,  109 

Acephala.  headless  molluscs,  95 

Acmeta,  27 

Actinia,  a  sea  anemone,  42 

Adaptive  characters,  10 

Adductor  muscles,  83 

Agrites   131 

Alcycnaria,  46 

Alcyonium,  46 

Alternation  of  generations,  40 

Ambulacra,  the  tube-feet  on  which 
sea-urchins  move,  49 

Amoeba,  22 

Amoebiform,  composed  of  protoplasm 
like  amoeba?. 

Amphipoda,  103 

Analogy,  similarity  in  function,  12 

Anelasma,  a  barnacle  which  lives  on 
living  fishes,  106 

Anemone,  sea,  42 

Animalcule,  a  minute  animal, 

Anomura,  107 

Antennae,  jointed  ieelers,  as  in  in- 
sects. 

Antennules,  99 

Anthrenus,  132 

Ant-lion,  127 

Ants,  127,  135 

Aphaniptera,  fleas,  128 

Aphides.  123 

Arachnoidea,  98,  108 


CAL 

Arenicola,  the  lug  bait,  71 
Arthrppoda,  14,  96 
Asc.-u-is,  round  worms,  65 
Assimilation,   the  process  wheieby 

food  is  converted  into  blood. 
Auricles,  94 

•DACTERIUM,  the  walking-stick 
•*-^     insect,   also    the   most   minute 

protoplasmic  particles,  125 
Falani,  acorn  shells,  106 
Barnacles,  106 
Fees,  134 
Beetles,  131 
Bilateral    symmetry,   equality    and 

proportion  of  the  two  correspond- 
ing sides  of  an  animal. 
Bivalves,  80 
Blood,  2 

Borlasia,  a  large  sea  worm,  60 
Brachiopoda,  80 
Brachyura,  108 
Branchiae,  gills. 
Branchiopoda,  104 
Breathing,     the    process     whereby 

oxygen  is  taken  in  to  aerate  the 

blo^L 

Bryozoa,  74 
Bugs,  123 
Butterflies,  129 
Byssus,  a  fibrous  material  whereby 

mussels  and  other  molluscs  anchor 

themselves,  84 


'ADDIS  FLIES,  127 

'     Calcareous,  consisting  of  lime. 


138 


Index  and  Glossary. 


CAL 

Calcified,   being  impregnated  with 

salts  of  lime 
Cantharis,  132 
Capsule,  24 
Cardo,  part  of  the  mouth  of  an  in- 

sect, 117 

Carnivorous,  flesh-eating. 
Caryophylla,  44 
Caterpillar,  121 
Cells,  2 

Centipedes,  112 
Cephalophora,  85 
Cephalopoda,.  90    . 
Cephaiothorax,  100 
Chaetopoda,  bristle-footed  worms.  90 
Chalk,  21 

Chamber,  atrial,  76 
Chelae,  the  pincers  or  first  pair  of 

abdominal  feet  of  a  crab  or  lobster, 

100 

Chelecerae,  the  pincers  or  mandibular 

palps  of  a  scorpion,  io3 
Chelifer,  112 
Chitin,  a  hard  material  which  forms 

the  outer  layer  of  insects,  96 
Chiton,  amultivalve  shell,  89 
Chrysalis,  122 
Chrysaora,  39 
Cilia,  minute  vibratile  hairs  made  of 

protoplasm,  3 
Cirripedia,     barnacles     and    acorn 

shells,  106 
Classification,  10 
Cliona,  a  boring  sponge,  31 
Cloaca,   the  excretory  chamber    of 

animals,  56 
Clypeus,  117 
Cnidae,  the  thread  cells  or  stinging 

cells  of  jellyfishes,  33 
Coccinella,  the  ladybird,  131 
Cochineal  insect,  124 
Cockle,  85 
Cockroaches,  125 
Cocoon,  121 
Coelenterata,  14,  32 
Coenosarc,  35,  45 
Coleoptera,  131 
Colonies,  clusters  of  animals  united 

on  a  common  stalk. 
Colorado  beetle,  131 
Colpoda,  28 
Commensals,  17 
Contractile  vesi  cle,  26 


Cornea,  108 

Cor  juula,    106 


EPI 

Costae,  119 
Cotylidea,  60 
Coxa, 119 
Crayfish,  98 
Crinoidea,  49 
Crustacea,  97,  98 
Ctenophora,  41 
Cucumaria,  56 
Cuttlefishes,  90 
Cyclops,  104 

Cyst,  .a  membranous  sac. 
Cystic,  possessing  a  sac-like  mem* 
branous  envelope. 

T^ADDY-LONG-LEGS,  129 

Daphnia,  103 

Decapoda,  107 

Deilelphila,  130 

Dentalium,  86,  88 

Dermesles,  132 

Differentiation,  the  setting  apart  of 
separate  tissues  for  different  pur- 
poses. 

Diptera,  128 

Distoma,  63 

Distribution,  15 

Dorsal,  71 

Doryphora,  132 

Dragonflies,  115,  126 

pARWIG,  124 

-1-'     Echinocardium,  55 

Echinodermata,  14,  47 

Echinoidea,  53 

Echinus,  53 

Ectoderm,  32 1 

Edriophthalmia,  an  order  of  crus- 
taceans, 108 

Elater,  the  glow-worm,  120 

Embryo,  the  immature  condition  of 
an  animal,  as  developing  from  the 

eg?'.8 

tncnmtes,  49 

Encystation,  the  condition  of  being 
enclosed  in  a  cyst  or  enveloping 
layer,  23 

Endoderm,  the  inner  layer  of  jelly- 
fishes,  sea  anemones,  &c.,  32 

Endoskeleton,  an  internal  firm 
framework  of  bones  or  gristles 
for  the  support  of  the  organism, 
96 

Epeira,  the  garden  or  geometrical 
spider,  in 

Epicranium,  part  of  an  insect's  head, 
117 


Index  and  Glossary. 


139 


EUP 

Etiplectella,  a  sponge  called  Venus, 
flower-basket,  31 

Euplexoptera,  an  order  of  insects, 
including  earwigs,  124 

Euplotes,  a  minute  animalcule,  28 

Exoskeleton,  an  external  firm  frame- 
work for  the  purpose  of  protection 
or  support,  96 

"pAMILY,  a  group  of  genera,  n 

A  Fauna,  the  collective  name 
for  all  the  animals  of  a  country, 
15 

Feather  stars,  50 

Femur,  the  thish  bone  in  verte- 
brates, or  the  third  joint  of  an  in- 
sect's leg,  119 

Fission,  the  process  of  multiplication 
in  animals  by  splitting,  5 

Flagellata,  a  group  of  microscopic 
animals,  28 

Flagellum,  a  minute  vibratile  hair- 
like  filament  which  is  the  chief 
organ  of  locomotion  of  the  Flagel- 
lata. 

Fleas,  128 

Flies,  128 

Flukes,  parasitic  worms,  63 

Food,  i 

Foraminifera,  a  group  of  microscopic 
shells,  19 

Function,  the  office  performed  by 
any  organ  or  part  of  the  body,  3 

Fungia,  a  mushroom-like  coral,  46 

/"*  ALATHEA,  a  genus  of  bivalve 

*-*    shells,  83 

Galea,    part   of  an    insect's    head, 

1 17  (fig.) 
Gall-flies,   the   flies  which  produce 

nut-galls  on  oaks,  &c. 
Gaily  worms,  112 
Ganglion,  a   swelling    on    a    nerve 

which    acts   as  a  centre    for  the 

evolution  of  nerve-force. 
Gasteropoda,  a  class  of  molluscs,  89 
Gemmation,   multiplication   by    the 

production  of  buds,  5 
Genus,   a  group    of   closely    allied 

species  un't»d  under  a  common 

name,  n 
Gephyrea,  a  group  of  marine  worms, 

Gills,  vascular  organs  which  are 
titled  for  aerating  the  blood  which 


KOI 

they  contain,  by  means  of  the  air 
dissolved  in  the  water  which  bathes 
them. 

Gizzard,  a  stomach  with  thick  mus- 
cular walls. 

Globigerina,  a  minute  shell,  18 
Gordiaceae,  threadworms,  68 
Gorgonia,  a  horny  coral,  46 
Grantia,  a  sponge,  32 
Gregarinae,    microscopic    parasites, 


TLJ  AIRY-BAIT.  71 

L     Halichondria,  a  sponge,  32 
Heliophrys,  22 
Heliozoa,  minute  animals  found  in 

bog  pools,  22 
Hessian  fly,  129 
Hinga  of  shells,  83 
Hirudinea,  leeches,  68 
Holothuroidea,  sea  cucumbers,  56 
Host,   an   animal    inhabited    by    a 

parasite. 

Hyalonema,  a  sponge,  31 
Hydra,  a  minute  fresh  water  polype, 

32 
Hydroida,  animals  like  the  hydra, 

34 

Hymenoptera,   an   order  of  insects, 
including  ants  and  bees,  132 

JCHNEUMON,  a  group  of  flies, 

Imago,  the  perfect  or  adult  state  of 

an  insect,  122 
Infusoria,  animals  found  in  stagnant 

waters,  25 
Insecta,  98 

Integument,  the  skin  of  an  animal. 
Iridescent,     producing    a    play    of 

colours  by  decomposing  incident 

rays  of  light 

Isis,  a  genus  of  corals,  46 
Isopoda,   an   order  of  crustaceans, 

including     woodlice     and     their 

allies,  103 


ELLY-FISHES,  3 


T/-OINOSITES.    animals    which. 
1  *•         live  on,  and  feed  with,  their 
hosts,  17 


140 


Index  and  Glossarv. 


LAB 

T  ABIUM,   the   lower   lip  of  an 

•L/        insect's  mouth,  1 16 

Labrum,  the  upper  lip  of  an  insect's 
mouth,  116 

Lac  insect,  124 

Lacunae,  interspaces  between  tis- 
sues. 

Ladybird,  131 

Lameilibranchs,  bivalve  molluscs, 
such  as  the  oyster,  81 

Lampyris,  the  firefly,  120 

Larva,  the  first  active  stage  of  an 
animal  while  as  yet  immature, 

T2I 

Leaf-roller  moths,  129 
Leeches,  68 
Lepidoptera,  129 

Ligament,   a   fibrous  band   uniting 

two  parts. 
Ligula,  part  of  the  so-called  tongue 

of  an  insect,  117 
Limulus,  the  king  crab,  103 
Lingula,  the  duck-hill  shell,  81 
Lithobius,   the  common  centipede, 

"1 

Locusts,  125 
Lug-bait,  71 
Lymexylon,  a  wood-boring  beetle, 


TV/TACRURA,  lobsters,  107 

***      Madrepores,      reef  -  building 

corals,  45 
Madreporiform  plate,  a  rough  plate 

on  the  surface  of  star-fishes,  52 
Magosphaera,  21 
Malacobdella,  a  leech,  69 
Malpighian  glands,  glands  in  insects, 

named  after  their   first  describer, 

Malpighi,  120 
Mandibles,  the  second  pair  of  jaws 

in  insects,  TOO 
Mantle,  the  leathery  outer    ayer  n 

molluscs,  14,  79 
Mason  spiders,  in 
Maxilla,  100 

Meandrina,  brain  coral,  46 
Medusa,  a  jelly-fish,  40 
Medusoids,    detached     portions    of 

hydroids  which  resemble  medusae, 

Meloe,  132 

Mentum,  part  of  an  insect's  mouth, 

118 
Mermis,  66 


ORT 

Mesenteries,  folds  of  membrane  sus- 
pending the  digestive  sac,  43 

Metamorphoses,  changes  undergone 
by  an  animal  in  its  development 
from  its  larval  to  its  perfect  state. 

Metazoa,  animals  with  an  internal 
cavity,  28 

Millepedes,  114 

Mimicry  in  animals,  12 

Mites,  109 

Mollusca,  14,  78 

Monads,  small  fl  gel'ate  animals,  28 

Monera,  the  simplest  known  ani- 
mals, 21 

Monocystis,  a  gregarine,  23 

Morphology.the  science  which  treats 
of  the  form*  of  animal  organisms,  7 

Moss  polypes   74 

Moths,  130 

Muscles,  4 

Mussels,  85 

Myriopoda,  98,  112 


TVTAUPLIUS,  the  larval  stage  of 

A^     crustaceans,  104 

Nautilus,  the  most  complex  of 
molluscs,  92 

Nematelmia,  64 

Nemerteans,  marine  worms,  60 

Nerve,  4 

Neuromuscular  cells,  33 

Neuroptera,  an  order  of  insects,  127 

Noctiluca,  a  luminous  marine  ani- 
malcule, 27 

Nucleolus,  26 

Nucleus,  21 

Nutrition,  4 


/^vCULAR  plates,  plates  bearing 

V-/     eyes,  54 

Ocuhna,  a  coral,  45 

CEsophagus,  the  tube  which  conveys 
food  to  the  stomach,  65 

Oikosites,  parasites  which  live  with, 
but  do  not  feed  on,  their  host,  120 

Operculum,  the  lid  which  closes  the 
mouth  of  an  univalve  shell,  87 

Ophiolepis,  a  star-fish,  51 

Ophiurqidea,  star-fishes,  75 

Ophrydium,  27 

Optic  nerve,  the  nerve  which  con- 
nects the  eye  and  the  brain,  99 

Organism,  an  animal  made  up  of 
separate  organs  or  parts,  13 

Orthoptera,  an  order  of  insects,  125 


Index  and  Glossary. 


141 


osc 

Osculum,  the  mouths  in  sponges, 

Ostracoda,  minute  crustaceans,  107 

Ovipositor,  the  organ  whereby  in- 
sects deposit  their  eggs,  121 

Ovulation,  the  mode  of  reproduction 
by  the  development  of  eggs,  5 

Oxytricha,  25 

Oxyuris,  a  worm,  63 

Oyster,  85 


PALAEOZOIC,    the    age    of  the 

•••  world  in  which  the  oldest  fossil- 
bearing  rocks  were  formed, 

Pallial  line,  the  line  on  a  shell  indi- 
cating the  margin  of  the  mantle, 
83 

Palp,  a  feeler  or  jointed  appendage 
on  the  jaw  of  an  arthropod. 

Paraglossae,  part  of  an  insect's 
mouth,  117,  133 

Paramcecium,  a  common  infusory 
animalcule,  26 

Parasites,  17 

Pauropods,  114 

Pedicellariae,  jointed  pincer-like  ap- 
pendages to  the  mouth  in  Echino- 
dermata,  51 

Pedicelli,  small  sucking  feet  in  star- 
fishes, 49 

Pennatula,  a  sea-pen,  46 

Pennella,  a  parasitic  crustacean, 
105 

Pentastoma,  a  parasitic  mite,  10 

Pericardium,  the  space  of  the  body 
cavity  around  the  heart, 

Periplaneta,  the  cockroach,  125 

Pharynx,  the  upper  part  of  the  di- 
gestive tube  near  the  mouth. 

Physalia,  37 

Physiology,  the  science  which  treats 
of  the  functions  of  organs,  7 

Pixinia,  a  gregarine,  23 

Planula,  the  ciliated  embryo  of  a 
jelly-fish,  33 

Pluteus,  the  larval  stage  of  a  star- 
fish, 51 

Podophthalmia,  crabs,  &c.,  whose 
eyes  are  on  stalks,  107 

Podur«e,  124 

Poecilopoda,  king-crabs,  103 

Polycelis,  a  Uibellarian  worm,  59 

Polypites,  hydra-like  animals  when 

in  colonies,  35 
Polystomata,  28 


SEG 

Pores,  the  fine  openings  in  sponges, 
3° 

Postabdomen,  that  part  of  the  ab- 
domen behind  the  openings  of  the 
reproductive  organs,  101 

Proglottis,  one  of  the  mature  joints 
of  a  tape-worm,  61 

Protamoeba.  one  of  the  simplest 
known  animals,  21 

Protoplasm,  2 

Protoplasta,  amoebae,  22 

Protozoa,  14, 18 

Provisional  organs,  those  organs 
that  fulfil  a  temporary  function, 
and  then  disappear  or  waste,  8 

Pseudonavicellae,  23 

Pseudopodia,  3,  19 

Pteropoda,  89 

Ptinus,  132 

Pupa,  the  quiescent  stage  in  the 
life  of  a  butterfly  before  the  per- 
fect imago  condition  is  reached, 

121 

Pyrosoma,  a  luminous  marine  mol- 
lusc, 77 


•D  ADIOLARIA,  24 

1V    Raphiophora,  Neptune's  Cup, 

a  sponge,  31 
I     Reproduction,  5 

Rhizopods,  18 
i     Rhizostoma,  a  jelly-fish,  39 

Rhynchota,  an  order  of  insects,  in- 

eluding  bugs,  123 
Rotatoria,  wheel  animalcules,  66 
Rotifer,  a  common  wheel  animalcule, 

67 
Rudimental    organ,    an    imperfect, 

functionless  structure,  9 


C  ALPA,  a  pelagic  mollusc,  77 
**     Sandhoppers,      small      crusta- 
ceans, 105 
Scallops,  84 
Scaphopoda   an  order  of  molluscs, 

Scolopendra  a  centipede,  114 

Scolytus,  a  wood-boring  insect,  131 

Scorpion-flies   ^27 

Scorpions,  112 

Sea-cucumbers,  56 

Sea-glue,  25 

Sea-urchins,  47,  53 

Segment,  one  of  the   successional 


Index  and  Glossary. 


morphological  units  of  the  body  of 
a  jointed  animal,  13 

Segmental  organs,  excretory  tubes 
in  the  segments  of  worms,  58 

Serpula,  72 

Sertnlaria,  34 

Shell,  oo 

Silica,  flint. 

Silkworms,  130 

Siphon,  84 

Siphonophora,  38 

Siphuncle,  90 

Snail,  87 

Solen,  the  razor-shell,  84 

Specialisation,  setting  apaw  of  an 
organ  for  a  special  function,  and 
for  it  alone,  13 

Species,  a  group  of  identical  indi- 
viduals under  a  common  name,  n 

Spicules,  siliceous  or  calcareous 
masses  embedded  in  animal  tissues, 
31 

Spiders,  no 

Spinnerets,  in 

Spirorbis,  72 

Sponges,  29 

Spongilla,  a  freshwater  sponge,  31 

Spoon-worms,  67 

Star-fishes,  7,  47 

Stellerida,  50 

Stipes,  part  of  an  insect's  head,  117 

Stock,  the  common  sfcm  of  a  colony. 

Strepsiptera,  a  small  order  of  in- 
sects, 127 

Strongylocentrotus,  a  common  sea- 
urchin,  32  (fig.) 

Symmetry,  8 


T  JEN  I  A,  the  tapeworm,  60 
Tarsus,   the  last  joints  of  an 

insect's  leg,  115 
Teeth  of  sea  urchin,  54 
Tegenaria,  the  house  spider,  in 
Telspn,  the  middle  flap  of  a  lobster's 

tail,  loi 

Tenebrio,  the  meal-worm,  132 
Tentacles,  feelers,  32,  33 
Terebratula,  80 
Termites,  126 

Test,  a  shell  or  exoskeleton, 
Thalassicolla,  sea-glue,  a  group  of 

marine  protozoa,  25 
Thorax,  the  chest,  or  the  region  of 

the  body  of  an  insect  which  bears 

the  legs,  1 16 


VOR 

Thread-cells,  stinging  cells  of  jelly- 
fishes.  33 

Thrips,  125 

Thysanoptera,  an  order  of  insects, 
125 

Thysanura,  124 

Tibia,  part  of  an  insect's  leg,  115 

Ticks,  no 

Trachea;,  air-tubes  for    breathing, 


TraXeal3' 


lungs,  groups  of  tracheae 

compressed  together,  no 
Trematoda,   an    order  of   parasitic 

worms,  63 
Trepang,  an  edible  sea-cucumber, 

56 

Trichina,  a  parasitic  worm,  65 
Trichocephalus,  65 
Trichoptera,  an  order  of  insects,  127 
Trilobites,  104 
Trochal  disks,  the  ciliated  lobes  on 

the  heads  of  some  minute  worms, 

79 
Trochanter,  the  second  joint  in  the 

leg  of  an  insect,  119 
Troctes,  the  death-tick  insect,  125 
Tubipora,  the  organ-pipe  coral,  46 
Tunicates,  75 
Tunic,  75 
Turbellaria,  59 
Types,  ii 


TTNDIFFERENTIATED,     not 
*"'     separated     into       specialised 
parts. 


WACUOLES,    clear     spaces    in 
v      masses  of  protoplasm,  20 
Valves  of  shells,  80 
Ventral,    the    under    side    of    the 

body. 
Ventricle,  the  cavity  of   the  heart 

which  by  its  contraction  drives  on 

the  blood  in  the  circulation,  94 
Venus'  Flower  Basket,  a  sponge,  31 
Vermes,  worms,  14,  57 
Vertebrata,  14 
Viscera,    the    digestive    and    other 

internal    organs   of   the  body  of 

an  animal. 
Vorticella,  25,  27 


Index  and  Glossary. 


WAS 


WASPS,  134 

Water- boatmen,  127 
Water- fleas,  103 
Water-scorpions,  124 
Wax-glands,  134 
Whelk.  87 
White  ants  126 


ZOE 


Wire  worms,  131 
Woodlice,  103 


143 


VOEA,  the  larval    stage  of    the 
**    common  crab,  joa 


HANDBOOKS  for  Students  and  General  Readers. 

ZOOLOGY 

OF    THE 

VERTEBRATE  ANIMALS 


BY 

ALEX.    MACALISTER,   M.D. 

Professor  of  Zoology  and  Comparative  Anatomy  in  the 
University  of  Dublin. 


Specially  Revised  for  American  Stttdents 


A.  S.  PACKARD,  JR.,  M.D. 

Professor  of  Natural  History  in 
Brown   University 


NEW   YORK 
HENRY   HOLT   AND   COMPANY 

1878 


COPYRIGHT,  1878, 

BY 
HENRY    HOLT    &    CO. 


PRINTED    BY   TROW's    PRINTING    AND   BOOKBINDING  .CO.,  NEW   YORK. 


EXPLANATORY. 


THIS  Series  is  intended  to  meet  the  requirement  of 
brief  text-books  both  for  schools  and  for  adult  readers 
who  wish  to  review  or  expand  their  knowledge. 

The  grade  of  the  books  is  intermecliate  between  the 
so-called  "primers"  and  the  larger  works  professing 
to  present  quite  detailed  views  of  the  respective  sub- 
jects. 

Such  a  notion  as  a  person  beyond  childhood  re- 
quires  of  some  subjects,  it  is  difficult  and  perhaps 
impossible  to  convey  in  one  such  volume.  Therefore, 
occasionally  a  volume  is  given  to  each  of  the  main 
departments  into  which  a  subject  naturally  falls — for 
instance,  a  volume  to  the  Zoology  of  the  vertebrates, 
and  one  to  that  of  the  invertebrates.  While  this  ar- 
rangement supplies  a  compendious  treatment  for  those 
who  wish,  it  will  also  sometimes  enable  the  reader 
interested  in  only  a  portion  of  the  field  covered  by  a 
science,  to  study  the  part  he  is  interested  in,  without 
getting  a  book  covering  the  whole. 

Care  is  taken  to  bring  out  whatever  educational 
value  may  be  extracted  from  each  subject  without  im- 


vi  Explanatory. 

peding  the  exposition  of  it.  In  the  books  on  the 
sciences,  not  only  are  acquired  results  stated,  but  as 
full  explanation  as  possible  is  given  of  the  methods  of 
inquiry  and  reasoning  by  which  these  results  have 
been  obtained.  Consequently,  although  the  treatment 
of  each  subject  is  strictly  elementary,  the  fundamental 
facts  are  stated  and  discussed  with  the  fulness  needed 
to  place  their  scientific  significance  in  a  clear  light, 
and  to  show  the  relation  in  which  they  stand  to  the 
general  conclusions  of  science. 

Care  is  also  taken  that  each  book  admitted  to  the 
series  shall  either  be  the  work  of  a  recognized  author- 
ity, or  bear  the  unqualified  approval  of  such.  As  far 
as  practicable,  authors  are  selected  who  combine 
knowledge  of  their  subjects  with  experience  in  teach- 
ins:  them. 


PREFACE 


IT  has  been  the  Author's  design  in  this  volume  to 
present  in  as  simple  a  form  as  possible  the  leading 
characters  of  Vertebrate  Animals.  All  unnecessary 
technicalities  have  been  dispensed  with,  and  explana- 
tions have  been  given,  either  in  the  text  or  in  the 
glossary,  of  such  terms  as  have  been  unavoidably 
used. 

In  a  practical  science  such  as  Zoology,  it  is  only 
by  the  examination  of  specimens  that  any  knowledge 
of  the  science  worth  acquiring  can  be  obtained,  and 
the  function  of  a  book  is  to  assist  in  practical  study. 
This  has  been  borne  in  mind  in  compiling  these 
pages.  Great  care  has,  moreover,  been  taken  to  select 
only  such  facts  for  discussion  as  are  of  fundamental 


viii  Preface. 

importance.  As  types  of  the  different  classes  of  ver- 
tebrated  animals  are  easily  obtainable,  the  pupil  is 
recommended  to  verify  these  facts  for  himself. 

ALEXANDER  MACALISTER. 

ANATOMICAL  MUSEUM, 

UNIVERSITY  OF  DUBLIN, 
Oct.  2,  1877. 


CONTENTS. 


CHAPTER  I. 

CHARACTERS  OF  VERTEBRATE  ANIMALS.   ACRANIA. 

PAGH 
The  Vertebrate  Body— Notochord— Skeleton— Amphioxus.    .      I 

CHAPTER  II. 

CRANIOTA. 

The  Brain  and  Skull— Visceral  Arches— Limbs— Ribs— Liver- 
Heart— Segmentation       6 

CHAPTER  III. 

CLASS   I.    PISCES   (FISHES). 

General  Characters— Scales— Fins— Lateral  Line— Skeleton- 
Brain — Gills  and  Breathing — Swimming  Bladder — Eggs  .    II 

CHAPTER  IV. 

ORDER  I.  LAMPREYS.   ORDER  2.  SHARKS. 

Lampreys  or  Marsipobranchs— Selachia  or   Sharks— Placoid 
Scales -Egg  Capsules— Sawfishes— Skates        ...     22 
a 


x  Contents. 

CHAPTER  V. 

ORDER  3.    GANOID  FISHES.      ORDER  4.    BONY  FISHES. 

ORDER  5.    DIPNOI. 

PAGH 

Ganoids  —  Scales  —  Isinglass  —  Teleostei — Sub-order,  Physo- 
stomi  —  Sub-order,  Anacanthini  —  Sub-order,  Acantho- 
pteri — Sub-order,  Pharyngognathi — Sub-order,  Lopho- 
branchii — Sub-order,  Plectognathi — Dipnoi  .  .  .26 

CHAPTER  VI. 

CLASS  2.   AMPHIBIA. 
General  Characters— Respiration— Skeleton     ....    34 

CHAPTER  VII. 

CLASSIFICATION  OF  AMPHIBIA. 

Order  i,  Gymnophiona — Labyrinthodonts — Order  2,  Urodela — 
Caducous  and  Perennial  Gills— Order  3,  Anura  .  .  37 

CHAPTER   VIII. 

CLASS   3.     REPTILES. 

General  Characters 40 

CHAPTER  IX. 

LIZARDS  AND  SNAKES. 

Order  i,  Lacertilia — Chamaeleons— Order  2,  Ophidia  or  Snakes 
— Venomous  Snakes  and  their  Poison-Apparatus  .  .  42 

CHAPTER  X. 

TORTOISES  AND   CROCODILES. 

Order  3,  Chelonia  or  Tortoises— Order  4,  Crocodilia       .        .    49 


Contents.  xi 

CHAPTER  XI. 

CLASS  4.   AVES  (BIRDS). 

PAGB 

General  Characters— Feathers  and  Feather  Tracts— Skeleton- 
Muscles— Digestive  Organs— Heart  and  Lungs— Eye—- 
Eggs   52 

CHAPTER  XII. 

CLASSIFICATION  OF  BIRDS. 

Sub-class  i,  Ratidae— Sub-class  2,  Carinatae— Order  i,  Psittaci 
or  Parrots — Order  2,  Coccygomorphae  or  Cuckoos — Order 
3,  Pici  or  Woodpeckers — Order  4,  Macrochires  or  Swifts 
and  Humming-Birds — Order  5,  Passeres  or  Perching  Birds 
— Order  6,  Raptores  or  Birds  of  Prey  ....  62 

CHAPTER  XIH. 

CLASSIFICATION  OF  BIRDS  (continued}. 

Order  7,  Gyrantes  or  Pigeons — Order  8,  Rasores  or  Scraping 
Birds  —  Order  9,  Grallas  or  Snipes  and  Cranes — Order 
10,  Ciconias  or  Storks — Order  u,  Lamellirostres  or  Ducks 
and  Geese — Order  12,  Longipennes  or  Gulls — Order  13, 
Steganopodes  or  Pelicans — Order  14,  Pygopodes  or 
Penguins  and  Auks 69 

CHAPTER   XIV. 

CLASS   5.     MAMMALIA. 

General  Characters— Laws— Skeleton— Teeth  — Dental  For- 
mulae   74 

CHAPTER  XV. 

CLASSIFICATION  OF  MAMMALS. 
Order  i,  Monotremata — Order  2,  Marsupialia  or  Kangaroos  .    79 


xii  Contents. 

CHAPTER  XVI. 

PLACENTAL  MAMMALS. 

PAGB 

General  Characters — Order  3,  Edentata  or  Ant-eaters  and 
Armadillos — Order  4,  Bradypoda  or  Sloths — Order  5, 
Sirenia  or  Manatees — Order  6,  Ungulata  or  Hoofed 
Animals — Unsymmetrically-toed  Ungulates  —  Even-toed 
Ungulates— Bunodonts— Ruminants .....  85 

CHAPTER  XVII. 

PLACENTAL  MAMMALS   (continued). 

Order  7,  Cetacea  or  Whales— Order  8,  Pinnipedia  or  Seals- 
Order  9,  Carnivora  or  Flesh-Eaters — Dogs — Cats — Bears — 
Order  10,  Hyracoidea — Order  11,  Rodentia — Order  12, 
Proboscidea  or  Elephants 99 

CHAPTER  XVIII. 

Order  13,  Prosimii  or  Lemurs — Order  14,  Insectivora,  Moles, 

Hedgehogs,  etc.— Order  15,  Chiroptera  or  Bats        .        .  113 

CHAPTER  XIX. 

Order  16,  Primates— Marmosets— American  Monkeys— Old- 
World  Monkeys — Man — Races  of  Man  .  .  .  .118 

INDEX  and  GLOSSARY  .  125 


VERTEBRATA. 

CHAPTER  I. 

CHARACTERS  OF  VERTEBRATE  ANIMALS.   ACRANIA. 

~*  i.  Introductory.— The  animals  which  make  up  the 
sub-kingdom  Vertebrata  are  the  fishes,  reptiles,  birds, 
and  quadrupeds ;  and  as  they  present  to  us  a  greater 
number  of  interesting  points  in  structure,  function,  and 
habits  than  all  the  other  sub -kingdoms  put  together, 
and  as  they  are  for  the  most  part  of  large  size  and  of 
complex  organisation,  they  require  a  more  careful  and 
detailed  study  than  do  the  animals  which  make  up  the 
other  sub-kingdoms.  On  this  account,  Vertebrata, 
though  in  reality  constituting  only  a  subdivision  equi- 
valent to  any  of  the  other  sub-kingdoms,  such  as 
Mollusca,  Polystomata,  or  Vermes,  are  yet  often  treated, 
and  naturally  so,  as  if  they  equalled  all  the  other  sub- 
kingdoms  collectively. 

2.  General  characters  of  vertebrate  animals. — 
Every  vertebrate  animal  possesses   in  the  centre   of 
its  body  an  axis  or  rod  of  cartilage,  which   forms  a 
B 


2  Vertebrate 

skeleton  or  support ;  below l  is  a  longitudinal  body- 
cavity,  containing  the  organs  of  digestion,  circulation, 
respiration,  &c. ;  above  is  a  second,  smaller,  longitu- 
dinal cavity  or  canal,  in  which  lie  the  brain  and 
spinal  marrow,  the  central  organs  of  the  nervous 
system;  these  send  out  laterally  along  their  whole 
extent  numerous  pairs  of  nerve-cords  to  supply  the 
different  parts  of  the  body.  Thus  on  cross-section 
the  body  of  a  vertebrate  animal  appears  like  two 
tubes,  the  smaller  being  above  the  larger,  and  the 
cartilaginous  axis  appears  in  the  middle  of  the 
horizontal  partition  which  divides  them  from  each 
other. 

In  the  young  conditions  of  the  tunicated  worms 
there  is  an  approach  to  this  arrangement,  but  in  these 
the  gristly  rod  does  not  extend  sufficiently  far  for- 
ward to  separate  the  neural  (or  nervous  system- 
holding)  and  visceral  cavities. 

To  the  central  axis  of  cartilage  the  name  notochord 
is  given,  and  it  is  enveloped  in  a  sheath  of  several 
layers.  In  the  majority  of  vertebrates  the  notochord 
is  present  only  as  a  temporary  and  transitory  structure, 
for,  in  the  process  of  growth,  parts  of  its  sheath  enlarge 
and  encroach  on  the  axis  itself,  so  as  to  obliterate 
it  eventually  in  whole  or  in  part.  These  enlarge- 
ments begin  in  the  form  of  a  succession  of  paired 
lateral  thickenings  along  the  whole  length  of  the 
sheath,  which  extend  above  and  below  the  notochord, 
and  become  converted  into  rings  around  it,  and 
ultimately  by  extension  inwards  they  become  discs. 

>  The  animal  is  supposed  to  be  placed  with  its  length  hori- 
zontal and  its  mouth  forwards. 


General  Characters  of  Vertebrates.  3 

The  chain  of  these  rings  or  disks,  around  or  replacing 
the  notochord,  which  forms  the  axis  in  the  adult  stage 
of  all  but  the  lowest  of  the  vertebrates,  is  called  the 
vertebral  column,  and  each  disk,  with  the  parts  im- 
mediately joined  to  it,  is  called  a  vertebra  (fig.  2). 

Each  vertebra  has  attached  to  it  behind  a  ring  or 
arch  (made  up  of  two  lateral  projections  or  processes) 
which  surrounds  the  spinal  marrow,  and  forms  the 
wall  of  the  neural  cavity.  This  arch  is  called  the 
neural  arch. 

The  mouth  opens  at  the  foremost  end  of  the  body 
in  all  vertebrates,  and  communicates  internally  with  a 
cavity  called  the  pharynx,  on  whose  walls,  directly  or 
indirectly,  the  blood-vessels  are  arranged  for  the 
purposes  of  respiration.  This  part  of  the  digestive 
canal !  is  pierced  by  slits  at  some  period  hi  the  life  of 
each  vertebrate. 

Below  the  pharynx  is  a  narrow  part  of  the  diges- 
tive canal,  called  the  oesophagus,  which  passes  between 
the  spinal  column  above  and  the  heart  below,  and 
leads  into  the  stomach,  from  whence  the  intestinal 
canal  is  continued,  to  open  at  the  posterior  end  of 
the  body  ;  directly  below  the  stomach  the  duct  of  the 
liver  opens  in  all  vertebrates,  and  this  organ  is 
peculiar  in  this  sub-kingdom,  in  that  the  vein  which 
conveys  the  impure  blood  back  from  the  digestive 
organs  enters  this  gland  and  breaks  up  within  it  into 
a  network  of  fine  vessels,  which,  reuniting,  pass  back 
from  hence  to  the  heart.  The  vessel  which  thus 

1  The  digestive  or  alimentary  canal   is   a   tube  traversing 
the  whole  length  of  the  body,  in  which  the  food  is  digested, 
and  its  nourishing  part  taken  into  the  blood. 
B  2 


4  Vertebrata. 

conveys  the  blood  from  the  alimentary  canal  to  the 
liver  is  called  the  vena  portce. 

3.  Primary  divisions  of  vertebrates  (headless 
form). — There  are  two  primary  divisions  of  vertebrate 
animals  ;  the  first  of  these  includes  only  one  form,  and 
that  the  smallest  and  simplest  in  the  sub-kingdom, 
remarkable  principally  for  its  extremely  simple  organ- 
isation. This  little  creature  is  named  the  lancelet,  or 
technically  the  Amphioxus  lanceolatus,  and  is  so  called 
on  account  of  its  lancet-like  shape,  and  from  its  being 
pointed  at  both  ends.  It  is  a  small,  flattened,  fish-like 
animal,  about  an  inch  and  a  half  long,  about  a  quarter 
of  an  inch  in  depth  and  an  eighth  in  thickness,  found 
in  sandbanks  in  our  own  seas.  It  has  been  taken 
in  abundance  off  the  coasts  of  North  Carolina  and 
Florida,  off  the  S.W.  coast  of  Ireland,  in  the  Mediter- 
ranean, and  in  the  Indian  and  Pacific  Oceans. 

This  animal  has  no  head,  and  the  notochord 
stretches  from  the  front  to  the  hinder  point ;  the 
neural  canal  and  its  enclosed  spinal  marrow  likewise 
extend  for  the  whole  length.  The  mouth  is  a  longi- 
tudinal slit,  bordered  with  stiff,  bristle-like  filaments ; 


'      >'  T=-T5- 

Diagram  of  Amphioxus. 

a,  mouth;   6,  f,  g,  respiratory  region ;    c,  body  cavity  ;   d,  liver  ;   e,  heart; 
/&-/,  digestive  canal ;  /,  notochord  ;  **,  spinal  marrow. 

and  the  pharynx  has  many  lateral  slits  in  its  wall, 


The  Lancclet.  5 

through  which  the  water  which  enters  the  mouth 
escapes  into  the  space  between  the  wall  of  the  body 
and  that  of  the  pharynx.  To  this  space  the  name 
'  atrium '  is  given,  and  it  opens  externally  by  a  median 
pore  or  outlet  placed  on  the  under  edge,  and  in  front 
of  the  end  of  the  intestine  (fig.  i,». 

The  liver  is  a  simple  sac,  and  the  heart  is  a  single  di- 
lated tube(^),  like  that  of  some  worms;  it  sends  branches 
backwards  to  the  pharyngeal  wall,  one  along  each  slit, 
and  these  join  dorsally  below  the  notochord,  making 
a  dorsal  aorta  or  large  blood-vessel,  which  gives  off 
branches  to  the  different  parts  of  the  body. 

Though  there  is  no  brain,  yet  two  of  the  foremost 
of  the  many  nerves  emitted  from  the  spinal  marrow 
supply  structures  which  may  be  regarded  as  rudimen- 
tary sense-organs.  Thus  there  is  in  the  middle  of  the 
foremost  end  of  the  animal  a  small  pit,  possibly  an 
organ  of  smell,  and  two  or  more  lateral  pigment-spots 
in  front  of  and  above  the  mouth,  which  may  be  organs 
of  sight  There  is  a  narrow  membranous  fringe  or  fin 
around  the  tail,  but  there  are  no  limbs,  and  the  blood 
is  colourless. 

The  division  of  Vertebrata  which  contains  this  sin- 
gularly aberrant  form  is  named  Acrania  (headless),  to 
distinguish  it  from  that  which  includes  the  entire  re- 
maining series,  which  is  called  Craniola  (head-bearing), 


6  Vertebrata. 

CHAPTER  II. 

CRANIOTA. 

4.  General  characters  of  head-bearing  vertebrates. 

The  head-bearing  vertebrates  are  characterised  by 
the  enlargement  of  the  anterior  end  of  the  central 
axis  of  the  nervous  system  into  a  series  of  swellings 
which  collectively  make  up  the  brain.  To  contain 
this  brain  the  fore  part  of  the  neural  canal  is  enor- 
mously dilated,  and  its  walls  are  converted  into  a 
gristly,  membranous,  or  bony  case,  called  the  skull, 
and  in  this  part  of  the  body  the  organs  of  sense  are 
chiefly  seated.  The  brain  in  its  simplest  form  con- 
sists of  three  thick-walled  cavities  in  a  series  from 
before  backwards,  the  walls  of  the  three  being  named 
respectively  the  fore,  mid,  and  hind  brain.  The  rest 
of  the  neural  canal  behind  the  skull  remains  as  a 
narrow  tube  enclosed  in  the  canal,  which  is  bounded 
by  the  neural  arches  of  the  vertebrae.  In  the  sides 
of  the  wall  of  the  cranial  or  skull  cavity  the  organs  of 
the  special  senses  are  placed  in  a  series  from  before 
backwards  ;  foremost  of  them  is  the  organ  of  smell ; 
secondly,  that  of  sight ;  thirdly,  that  of  hearing.  Each 
of  these  organs  consists  primarily  of  a  pouch  of  skin 
bulging  towards  the  inside  of  the  body,  and  receiving 
a  nerve  from  the  brain.  Passing  out  from  the  brain 
there  are  also  other  nerves,  which  are  distributed  to  the 
parts  of  the  foremost  end  of  the  body.  Around  these 
organs  and  nerves  the  cartilage  which  forms  the  primi- 
tive skull  becomes  disposed  so  as  to  protect  them;  and 


Visceral  Arches.  7 

when,  as  is  often  the  case,  the  cartilage  becomes  con- 
verted into  bone,  the  several  pieces  of  which  the  osseous 
skull  consists  are  so  grouped  around  these  nerves  and 
sense  organs  that  the  bony  cranium  appears  as  if  its 
bones  were  arranged  in  a  succession  of  segments. 
These  have  been  mistaken  for  true  vertebral  divisions, 
but  are  really  due  to  a  secondary  grouping  of  parts  in 
the  course  of  growth,  and  are  not  primary  morpho- 
logical elements.  Appended  to  the  under  or  mouth 
side  of  the  cranium,  and  to  the  fore  part  of  the 
vertebral  column,  we  find  a  series  of  lateral  arches, 
which  unite  below  in  the  medial  line,  and  thus 
close  in  the  sub- vertebral  cavity  in  front  To  these 
arches  the  name  'visceral  arches/  is  given  ;  and  very 
often  between  these  arches  there  are  slits  opening 
inwards  ;  these  are  called  visceral  slits.  The  number 
of  these  arches  varies  in  many  vertebrates,  but  there 
may  be  as  many  as  ten  or  twelve.  The  foremost  is  in 
front  of  the  part  of  the  skull  which  begins  at  the  front 
end  of  the  notochord  (for  this  structure  does  not  in 
craniotes  extend  beyond  the  region  of  the  mid-brain), 
and  its  two  elements  pass  forwards  in  the  middle 
line  to  unite  in  front;  to  these  the  name  cornua 
trabeculcK  is  given.  The  second  arch  lies  behind, 
below,  and  a  little  outside  the  cornua  trabeculse,  and 
forms  part  of  the  deeper  or  palatine  portion  of  the 
upper  jaw  in  most  vertebrates  (or  the  whole  upper 
jaw  in  sharks) ;  its  lower  end  forms  the  lower  jaw,  or 
parts  thereof.  The  third  or  hyoid  arch  is  that  bony 
system  on  which  the  tongue  is  based  ;  and  the  suc- 
ceeding ones  can  be  easily  distinguished  in  fishes  as 
the  arches  of  bones  which  bear  the  gills,  but,  except 


8  Vertebrata. 

the  foremost  of  this  set,  the  others  are  rudimental  in 
the  higher  animals.  The  visceral  slit  between  the  first 
and  second  of  these  arches  is  the  mouth ;  the  other 
visceral  slits  remain  either  as  the  gill  fissures  in  fishes, 
or  else  become  closed  at  an  extremely  early  period 
of  embryonic  life.  The  remnant  of  the  first  pair  of 
visceral  slits  behind  the  mouth  we  find  in  the  form  of 
the  ear  passages  in  higher  vertebrates.  These  visceral 
arches  never  extend  backwards  behind  the  heart. 

5.  Limbs  and  ribs. — Vertebrate  animals  have 
never  more  than  four  limbs,  which  are  placed  two  in 
front  and  two  behind.  The  fore  limbs  are  usually 
placed  a  short  way  behind  the  head  ;  the  hind  limbs 
at  or  immediately  behind  the  posterior  end  of  the 
visceral  cavity.  Each  limb  has  a  bony  or  gristly  axis 
or  skeleton,  and  this  consists  of  two  parts — first,  a 
girdle  or  half-zone  of  bone,  which  is  embedded  in  the 
lateral  muscles,  and  is  often  attached  to  the  vertebral 
column  ;  secondly,  a  limb  ray  or  projecting  part  made 
up  of  several  sets  of  cartilages  in  a  series.  Some 
vertebrates,  like  whales  and  some  lizards,  have  only 
two  fore  limbs  and  no  hind  limbs ;  others,  like  boas 
and  pythons,  have  rudimentary  hind  limbs  and  no  fore 
limbs;  others,  like  most  of  the  snakes,  have  no  limbs  at 
all.  These  limbs  are  always  turned  towards  the 
haemal  or  ventral  side  of  the  body. 

In  the  wall  of  the  visceral  cavity,  following  the 
visceral  arches,  but  quite  separate  from  them,  there 
are  usually  long  slender  bones,  jointed  at  the  back 
to  the  vertebral  column,  and  forming  supports  for 
the  wall  of  this  space.  These  bones  are  named 
ribs,  and  the  part  of  the  body  surrounded  by  them 


Ribs  and  Secreting  Organs. 


FIG.  2. 


Diagram  of  a  vertebra,  with  its 
body  (5  ,  rib  (7),  and  breast  bone  (6). 


is  called  the  thorax  ;  the  region  between  the  thorax 
and  the  head  is  called  the  neck — a  very  short  space 
in  fishes  and  whales,  long 
in  many  birds.  The  part 
of  the  vertebral  column 
which  projects  behind  the 
visceral  cavity  is  named 
the  caudal  or  tail  region, 
and  in  it  there  are  usu- 
ally V-like  bony  arches, 
suspended  to  the  lower 
surface  of  the  vertebral 
bodies,  within  which  a 
caudal  blood-vessel  is  pro- 
tected. 

6.  Secreting1  organs. — All  vertebrate  animals  of 
this  division  have  a  solid  glandular  liver  for  secreting 
the  bile,  an  important  fluid  used  in  the  process  of 
digestion.  They  have  all  red  blood,  the  colour  de- 
pending on  the  presence  of  certain  minute  coloured 
corpuscles.  The  circulation  of  the  blood  is  maintained 
by  a  muscular  heart,  which  never  possesses  fewer  than 
two  chambers,  one  of  which  is  for  the  collection  and 
reception  of  the  blood  from  the  veins,  and  is  called 
the  auricle ;  the  other,  which  is  named  the  ventricle, 
propels  the  blood  into  the  large  blood-vessels  or  aortic 
arches,  of  which  there  are  usually  (in  some  period  of 
life  at  least)  more  than  three  pairs. 

In  vertebrates  the  lining  membrane  of  the  mouth 
(which  is  named  the  mucous  membrane),  clothing  the 
upper  and  lower  jaws,  and  sometimes  the  similar 
membrane  over  other  bones,  developes  processes  or 


io  Vertebrata. 

papillae,  which  become  converted  into  a  very  hard 
kind  of  bones  for  the  purpose  of  seizing  and  dividing 
their  food ;  these  are  known  as  teeth.  In  higher 
forms  these  become  rooted  in  the  subjacent  bones, 
but  in  all  cases  they  arise  as  papillae  of  the  mucous 
membrane. 

The  products  of  waste  (which  is  constantly  taking 
place)  are  got  rid  of  by  means  of  certain  purifying 
organs.  The  skin,  by  means  of  its  glands,  removes 
some  of  these  effete  matters ;  so  do  certain  areas  of 
the  pharynx,  richly  supplied  with  blood-vessels  from 
the  aortic  arches,  and  which  are  called  the  respiratory 
organs.  There  are  also  developed  certain  glandular 
tubes  in  the  hinder  portion  of  the  visceral  cavity,  of 
the  same  nature,  and  built  on  the  same  plan,  as  the 
segmental  tubes  of  worms,  which  eliminate  from  the 
blood  the  nitrogenised  waste  products  ;  these  organs 
are  called  kidneys. 

7.  Primary  and  secondary  segments. — In  the 
body  of  a  vertebrate  animal  there  is  to  be  seen  the 
remains  of  a  primary  segmentation  into  a  chain  of 
successional  divisions  ;  thus  many  organs  or  parts 
are  repeated  in  a  series,  such  as  the  vertebrae,  the 
nervous  system,  the  muscle  masses  (as  can  be  seen 
in  fishes),  and  the  tubes  which  constitute  the  kidney. 
At  the  same  time  there  is  such  a  tendency  to  con- 
centration noticeable  that  this  segmental  symmetry  is 
only  to  be  seen  in  the  lower  forms,  or  in  the  embryonic 
stages  of  the  higher,  secondary  modes  of  aggregation 
of  parts  masking  completely  the  original  systems  of 
segments.  For  example,  while  in  the  embryo  the 
primitive  vertebrae  can  be  distinguished  clearly  from 


Cephalization.  1 1 

each  other,  in  the  adult  what  appear  to  be  the  verte- 
bral segments  are  really  due  to  a  secondary  cleaving 
occurring  in  a  later  stage,  after  the  originally  separate 
primary  segments  have  become  fused. 

As  we  ascend  in  the  scale  of  complexity  among 
vertebrates,  we  find  as  a  rule  that  the  head  becomes 
more  and  more  highly  organised,  and  that  there  is  a 
tendency  towards  the  concentration  of  its  elements, 
and  that  the  fore  parts  of  the  body  become  more  and 
more  subservient  to  it  This  reaches  its  climax  in  man, 
where  we  find  the  anterior  pair  of  limbs  entirely  set 
apart  to  wait  on  the  head. 

There  are  five  classes  of  vertebrate  animals— fishes, 
amphibians,  reptiles,  birds,  and  mammals. 


CHAPTER  III. 
CLASS  i,  PISCES  (FISHES). 

8.  General  characters  of  fishes. — Fishes  consti- 
tute the  first  and  simplest  class  of  the  head-bearing 
vertebrates,  and,  like  the  simplest  forms  of  all  the 
other  sub- kingdoms,  they  are  aquatic  in  habit,  and 
all  their  organs  are  adapted  for  a  watery  home. 
Thus  in  shape  they  are  for  the  most  part  of  an 
elongated  flattened  outline,  pointed  in  front,  tapering 
behind,  so  as  to  afford  as  little  resistance  as  possible 
in  traversing  the  water  ;  the  fore  part  of  the  body,  or 
head,  is  joined  to  the  trunk  directly,  without  the  inter- 
vention of  a  narrow  neck,  and  to  the  hinder  ex- 


12  Vertebrata. 

tremity  of  the  vertebral  column  is  appended  a  flattened 
tail,  which,  by  moving  like  a  scull  or  screw-propeller, 
can  drive  the  body  forward.  The  limbs  are  also,  in 
fishes,  developed  into  fanlike  bars,  the  fins. 
-^  9.  Scales. — The  surface  of  the  body  in  fishes  has 
only  a  scanty  epidermis,  or  outer  layer  of  skin,  which  is 
generally  of  a  mucous  or  slimy  consistence;  beneath  this 
is  the  dermis,  or  inner  skin,  whose  surface  consists  of 
numerous  thin,  flattened  scales.  These  structures,  so 
characteristic  of  fishes,  are  composed  of  bony  plates, 
which  are  ossifications  of  flat  dermal  processes,  often 
containing  or  bearing  little  tooth-like  points,  composed 
of  the  same  material  as  true  teeth.  In  some  fishes,  like 
sharks,  the  entire  scale  consists  of  this  dentine  or  tooth 

FIG.  3. 


Placoid  scale  of  dog-fish  (vertical  section  magnified). 
«,  enamel  layer  ;  b,  dentine  of  spine  on  scale. 

structure  (fig.  3)  ;  in  others  the  bony  element,  which 
forms  around  the  tooth,  covers  or  entirely  supersedes 
the  dentinal,  but  in  its  essential  nature  the  coating  of 
scales  or  dermal  exoskeleton  of  fishes  may  be  regarded 
as  consisting  of  or  containing  ossified  papillae,  which 
in  their  structure  are  identical  with  the  tissue  of  ordi- 


Scales  and  Fins.  1 3 

nary  teeth.1     Many  scales  are  of  beautiful  forms,  and 
they  vary  very  much  in  outline  and  surface,  some- 

FlG.  4. 


Cycloid  scale  of  roach  magnified  ;  seen  in  section  A,  and  on  surface  B. 

times  being  flat  and  smooth-edged  (fig.  4),  or  else 
spinose,  ridged,  or  comblike  (fig.  5).  These  structures 
can  be  examined  and  their  varieties  observed  with  the 
aid  of  a  pocket-lens.  The  scales  of  the  pike,  sole, 
and  perch  are  especially  characteristic  forms. 

10.  Fins. — Along  the  middle  line  of  the  body  of  a 
fish  there  are  usually  developed  extensions  of  the  dermal 

1  It  would  perhaps  be  more  correct  to  say  that  teeth  are 
really  in  nature  a  special  set  of  dermal  papilla?  of  the  same 
nature  as  those  which  cover  the  surface  of  the  skin  in  some 
fishes,  ?nd  which,  covering  the  jaw  arches,  are  set  apart  for 
grasping  and  dividing  food  ;  but  the  relationship  is  put  con- 
versely, as  the  tooth  form  is  the  more  familiar. 


14  Vertebrata. 

exoskeleton  in  the  form  of  median  fins.     Of  these  one 
extends  along  the  upper  or  dorsal  edge,  and  is  named 
F  the  dorsal  fin,  consisting  of  a  suc- 

cession of  soft  and  branched  or 
spiny  and  hard  fin-rays  connected 
by  membrane.  The  other  is  pre- 
sent on  the  under  or  ventral  side 
of  the  body  behind  the  terminal 
opening  of  the  intestine ;  this  is 
called  the  anal  fin.  These  median 
fins,  though  apparently  single  and 

Ctenoid  scale.  >     .    * 

central,  are  in  reality  composed  of 
two  lateral  layers  placed  in  close  apposition. 

11.  Sense-organs  of  the  lateral  line. — Along  the 
line  of  greatest  convexity  of  each  side  of  the  body 
of  a  fish  there  is  a  lateral  line,  extending  from  be- 
hind  the  eye  to   the  side   of  the  tail.      This   con- 
sists of  a  row  of  scales,   each  pierced  by  a  minute 
tube  leading  into  a   small  simple  or  branched  sac 
filled  with  a  gelatinous  material,  in  which  the  extremity 
of  a  nerve  is  embedded.     These  are  organs  of  sense, 
and  are  probably  capable  of  being  impressed  by  several 
forms  of  vibration. 

1 2.  Backbone  and  tail. — The  vertebral  column  of 
fishes  usually  consists  of  a  chain  of  biconcave  vertebral 
bodies,  bearing  on  their  upper  surfaces  neural  arches 
which  are  surmounted  by  long  neural  spines.     On  the 
under  side  the  vertebrae  bear  ribs  towards  the  front, 
and  V-shaped  bones  towards  the  hinder  part  of  the 
body.     The  hindmost  of  the  tail  vertebrae  may  either 
gradually  diminish  to  a  point,  as  in  the  African  mud- 
fish (fig.  14),  or  they  may  undergo  modification,  being  re- 
placed by  a  rodlike  bone  which  turns  sharply  upwards, 


The  Sole. 


as  in  the  tails  of  most  of  the  bony  fishes.    The  median 
fin  is  continued  around  the  tail  end  of  the  vertebral 


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i 


column,  and  sometimes  appears  as  a  simple  uniform 
fringe  evenly  distributed  around  the  pointed  vertebraj 
axis,  or  else  the  whole  caudal  area  of  the  vertebral 
column  becomes  upturned  and 
the  tail  fin  forms  a  large  lobe 
on  the  under  surface  of  the 
axis  while  simply  margining  the 
end  of  the  caudal  vertebrae  ; 
such  a  tail  is  spoken  of  as*  an 
unequally  lobed  tail.  When,  as 
in  bony  fishes,  the  extremity  of 
the  spinal  column  becomes  con- 
verted into  a  single  bone,  then 
the  fin  borne  by  it  is  usually 
an  evenly  bilobed  tail,  such  as 
that  of  a  herring  or  salmon 
or  sole.  It  is,  however,  an  in- 
teresting fact  in  relation  to  this 
that  the  young  fry  of  the  salmon 
or  other  bony  fish  has  origi- 
nally a  tail  of  the  unevenly 
^  l0^6^  character,  which  by  the 
&y  \?  I  5  snortening  °f  tne  upper  part, 
and  the  expansion  of  the  lower 
lobe,  becomes  even,  as  we  find 
it  in  the  adult. 

In  the  simplest  fishes  the 
notochord  persists  through  life, 
and  such  fishes  have  generally  a  uniformly  fringed 
tail,  as  in  the  lampreys. 

The  structure  of  the  skull  differs  in  the  various 
subdivisions  of  the  class  :  in  some  it  is  a  simple  carti- 


Skull  of  Fishes.  17 

laginous  box,  as  in  lampreys  and  sharks;  in  others 
this  cartilaginous  box  is  covered  and  protected  by  a 
series  of  bony  dermal  plates,  as  in  the  sturgeon,  or 
the  whole  skull  may  be  made  up  of  a  number  of 
closely  articulated  and  perfectly  united  bony  pieces 
as  in  the  cod  (fig.  8).  In  this  case  it  must  be  re- 
membered that  these  bones  are  of  a  twofold  nature — 
first,  the  ossified  pieces  of  the  cartilage  of  which  the 
primitive  skull  consists,  and  which  surrounds  the  dif- 
ferent apertures  and  nerves,  forming  principally  the 
lateral  walls  of  the  skull ;  secondly,  the  ossified  plates 
of  membrane  which  are  the  equivalents  of  the  dermal 
bony  plates  of  the  sturgeon,  and  which  chiefly  make 
up  the  roof  and  floor  bones. 

Besides  the  skull  or  brain-case  proper,  the  head  of 
a  fish  consists  of  four  other  series  of  bones,  as  can  be 
seen  in  fig.  8.  These  are,  first,  those  of  the  upper  jaw 
arch,  sometimes  seven  in  number  on  each  side ; 
secondly,  those  of  the  lower  jaw  arch,  sometimes  four 
or  five  pairs  ;  thirdly,  those  of  the  gill  arches,  four,  five, 
or  six  pairs  of  arches  on  each  side,  each  consisting  of 
about  four  pairs  of  bones,  and  bearing  the  gills  These 
three  series  are  chiefly  ossifications  in  the  system  of 
visceral  arches  before  referred  to.  Besides  these,  there 
is  a  fourth  group  of  bones,  those  of  the  operculum  or 
gill  cover,  which  overlap  and  cover  the  gill  arches ; 
of  these  there  are  four  or  more,  making  up  the  gill 
cover  on  each  side.  It  is  thus  not  to  be  wondered  at 
that  the  skeleton  of  the  head  of  a  fish  presents  an 
appearance  of  great  complexity. 

The  limbs  of  fishes  are  converted  into  fins,  and  of 
these  there  are  usually  two  pairs.  The  fore  limbs,  or 
c 


i8 


Vertebrata. 


pectoral  fins,  are  placed  directly  behind  the  head,  to 
which  indeed  the  shoulder  girdle  is  in  most  fishes 
united  by  small  dermal  ossifications.  The  hind  limbs 
are  called  the  ventral  fins,  and  are  rarely  as  well  de- 


Skull  of  Cod. 

3,  supra-occipital  bone  ;  4,  opisthotic  ;  8,  post-temporal :  n,  frontal ;  9, 
parasphenoid  bone  ;  g,  g,  sub-orbital  bones  ;  22,  premaxilla  ;  21,  maxilla  ; 
24,  pterygoid  ;  28,  hyomandibular  ;  29,  articular  piece  of  lower  jaw  ;  23, 
dentary  bone  ;  39,  40,  41,  43,  hyoid  arch  ;  44,  branchio-stegal  rays;  34, 
35>  36,  37,  opercular  bones. 

veloped  as  the  fore  limbs,  and  the  pelvic  girdle  is 
seldom  attached  to  the  vertebral  column.  The  fins 
are  of  use  in  directing  the  motion  of  fishes,  while  the 
tail  is  the  principal  organ  of  propulsion. 


Brain  and  Heart  of  Fishes. 


13.  Internal  organs  of  fishes. — The  brain  of 
fishes  (fig.  9)  is  small,  not  filling  the  cranial  cavity. 
It  consists  of  a  succession  of  little  knobs  or  ganglia 
arranged  in  a  chain  from  before  backwards.  Of 
these  the  foremost  are  connected  with  the  sense  of 
smell,  the  second  consist 
of  the  fore- brain  hemi- 
spheres or  cerebrum,  the 
third  are  the  optic  lobes 
from  which  the  nerves  of 
sight  arise,  the  fourth  con- 
stitute the  mid-brain  and 
the  fifth  the  hind  brain. 

Beneath  and  behind 
the  head  lie  the  gills  (fig. 
10),  which  consist  of  nume- 
rous vascular  fringes  ar- 
ranged in  platelike  layers 
attached  to  the  visceral 
arches,  and  bathed  by  the 
water  which  enters  the 
mouth  and  escapes  through 
the  visceral  slits.  The  heart 
is  situated  in  the  middle  Brain  of  Cod. 

Of   What  We  might    Call    the  /,  nerves  of  sight;  k,  nerves  of  smell; 

.  ...  a,  foremost  lobe  of  brain  ;  c.  se- 

throat,  a  Very  Short  distance  cond   lobe  or  cerebrum  ;  /  cere 

u    U'     J        it.          i  •  bellum;  A,  hind  brain  or  medulla 

behind       the       lower      jaw.  oblongata ;  »,  fifth  pair  of  nerves ,; 

This    nrain     rnndstc;    nf   a  «,  nerves  of  hearing  ;  0,  ninth  pair 

>1SIS    01    a  of  nerves; /.tenth  or  vagus  nerve. 

thin-walled  auricle,  receiv- 
ing the  veins  which  convey  to  it  the  impure  blood 
from  the  body,  and  a  large  thick-walled  ventricle  for 
propelling  the  blood  into  the  gills.     This  latter  is 
ca 


2O 


Vertebrata. 


sometimes  prolonged  at  its  outlet  into  a  conical  part 


FIG.  10. 


full  of  valves,  called  the 
arterial  cone,  which  ends 
in  the  large  main  blood- 
vessel, or  aorta.  The 
arterial  cone  is  well  de- 
veloped in  sharks. 

Sometimes,  as  in 
most  of  our  common 
fishes,  the  aorta  at  its 


A,  the  aortic  bulb  ;  H.  heart  :  B, 
branchial  arches  ;  b,  branchial 
veins  returning  the  blood  to  A, 
the  aorta ;  v,  v,  the  ve.ns. 

B  shows  the  structure  of  one  of  the 
branchial  arches,  with  its  ap- 
pended gill  filaments,  be.  The 
blood  from  the  aortic  bulb 
passes  through  B,  the  branch- 
ial artery,  is  aerated  in  the  fila- 
ments be,  collected  and  returned 
by  b,  the  branchial  vein,  into  A, 
the  dorsal  aorta. 


8 


Diagram  of  the  circulation  in  a  fish. 


Circulation  in  Fishes.  21 

commencement  is  swollen  into  an  aortic  bulb,  from 
which  come  off  at  least  three  pairs  of  branchial  or 
gill  arteries  ;  these  pass  in  the  form  of  arches,  right 
and  left,  to  the  gills,  and  there  break  up  into  fine 
branches  in  the  soft,  fringe-like  folds.  Here  the 
blood,  being  exposed  to  the  air  dissolved  in  the  water, 
absorbs  oxygen  and  gives  out  carbonic  acid,  and  is 
thus  purified. 

The  purified  blood,  returning  from  the  gills  by  the 
branchial  veins ,  enters  the  dorsal  vessel  or  aorta, 
which  sends  it  to  the  different  organs  of  the  body  to 
supply  the  viscera. 

The  blood  of  fishes  is  generally  of  the  same 
temperature  as  the  medium  wherein  they  live,  or  only 
slightly  warmer,  and  hence  it  usually  feels  cold  to 
the  touch.  It  contains  corpuscles,  or  little  micro- 
scopic bodies,  of  an  oval  shape  and  with  a  central 
nucleus. 

Though  the  respiration  of  fishes  is  accomplished 
by  means  of  the  air  which  is  dissolved  in  water,  yet 
it  is  supplemented  in  some  of  them  by  direct  exposure 
of  the  gills  to  the  atmosphere,  and  some  fishes  are 
killed  if  prevented  from  rising  to  the  surface. 

In  most  fishes  there  is  a  large  sac  filled  with  air, 
placed  beneath  the  vertebral  column  at  the  anterior 
part  of  the  body  cavity,  and  communicating  by  a  duct 
with  the  digestive  organs.  This  is  called  the  swimming- 
bladder,  or  the  air-bladder,  and,  by  expanding  or 
compressing  it,  the  fish  can  rise  or  sink  in  the  water. 
This  sac  commences  its  existence  in  the  embryo  as 
an  outgrowth  from  the  neck  end  of  the  alimentary 
canal. 


22  Vertebrata. 

Fishes  are  oviparous,  that  is,  their  .young  are 
produced  from  eggs,  and  for  the  most  part  they  are 
enormously  prolific.  The  egg-organ  of  the  cod  some- 
times contains  over  a  million  eggs,  and  some  other 
fishes  are  equally  fruitful ;  the  eggs  are  of  small  size, 
and  contain  very  little  food  yolk.  The  majority  of 
fishes  are  marine  ;  those  found  in  fresh  water  are,  as 
a  rule,  simpler  in  organisation  and  retain  many  of  the 
embryonic  characters  of  the  class.  About  13,000 
different  species  of  fish  are  known,  and  they  are 
divided  into  five  orders. 


CHAPTER   IV. 


14.  Order  1,  Marsipobranchii  (Lampreys). — 
This,  tb<e  most  lowly  organised  order,  consists  of 
wormlike,  limbless,  scaleless  fishes  with  no  lower 
jaw,  a  circular  suctorial  mouth,  a  persistent  noto- 
chord,  and  gills  in  the  form  of  lateral  pouches.  They 
are  also  remarkable  among  fishes  for  having  circular 
blood  corpuscles. 

The  most  familiar  examples  are  the  little  fresh- 
water lamprey,  the  large  sea  lamprey,  and  that  curious 
parasite  the  glutinous  hag,  which,  by  means  of  its 
large,  jagged  tooth,  bores  its  way  into  the  body  of  the 
cod,  ling,  or  other  large  fish,  and  lives  therein,  feeding 
on  the  juices  of  its  prey.  In  all  these  there  is  but 


Lampreys  and  Sharks. 


one  median  pitlike  nostril,  and  the  hag  is  remarkable 
among  fishes  for  having  a  passage  of  communication 
between  the  bottom  of  this  pit  and  the  posterior  part 
of  the  cavity  of  the  mouth.  No  such  communication 
exists  in  other  fishes,  in  which  the  nose  is  a  simple 
depression  or  cavity  on  the  surface  of  the  head,  lined 
by  a  plaited  mucous  membrane  and  crossed  over  by 
a  bridge  of  skin.  The  teeth  in  lampreys  are  horny 
and  conical ;  they  are  shown  in  fig.  n. 

FIG. ii. 


w 
Head  of  lamprey  dissected. 


xicau  ui  Jiimprey  (uascoeu* 

a,  b,  c,  cartilages  of  the  mouth  ;  d,  e,f,g,  k,  muscles  attached 
to  the  cartilages. 

The  name  Marsipobranchii  is  given  to  this  group 
on  account  of  the  pouchlike  nature  of  the  gills,  which 
are  in  six  or  seven  pairs,  arranged  in  two  lateral  rows, 
and  open  by  small  holes  on  the  surface. 

15.  Order  2,  Selachia  (Sharks).— The  second 
order  includes  the  sharks  and  rays,  the  largest  indi- 
viduals in  the  entire  class  of  fishes  ;  but,  notwith- 
standing their  size,  these  exhibit  in  respect  to  many 
points  of  organisation  what  may  be  considered  as 


24  Vertebrata. 

elementary  characters— that  is,  they  display  in  their 
permanent  state  points  of  structure  which  other  more 
specialised  fishes  present  only  in  the  embryonic  stages. 
They  are  for  the  most  part  marine,  and  the  skeleton 
remains  almost  entirely  cartilaginous  and  never  be- 
comes truly  ossified.  The  notochord,  however,  rarely 
persists,  being  generally  replaced  by  an  axis  of  bicon- 
cave, often  calcified,  cartilaginous  disks  or  vertebral 
bodies. 

The  jaws  in  sharks  are  usually  placed  beneath,  not 
at  the  front  of,  the  prominent  snout,  and  they  are  both 
cartilaginous,  being,  in  fact,  two  parts  of  a  visceral  arch. 
The  gills  are  symmetrical  lateral  plates  of  vascular 
membrane,  interposed  between  pouches  which  have 
a  row  of  holes  or  slits  on  each  side,  opening  super- 
ficially on  the  side  of  the  neck,  and  internally  by  a 
row  of  perforations  into  the  pharynx. 

The  entire  surface  of  the  dermis  is  covered  with 
toothlike  papillae,  composed  of  true  tooth-tissue  or 
dentine,  and  these  over  the  jaw  arches  are  large  and 
developed  into  functional  teeth,  which  are  sometimes 
of  formidable  size  and  proportions.  There  are  several 
rows  of  these,  and  as  they  are  gradually  worn  away 
with  use,  they  replace  each  other  from  within  out- 
wards. This  form  of  dermal  scales  on  the  surface  of 
the  body  is  named  placoid  (fig.  3). 

The  vertebral  axis  is  prolonged  into  the  upper 
lobe  of  the  tail,  which  thus,  on  account  of  the  large 
size  of  the  lower  lobe,  belongs  to  the  unevenly  lobed 
or  heterocercal  type,  not  like  the  uniform  marginal 
fringe  of  the  lampreys.  The  fins  are  often  armed 
with  single,  strong,  and  sometimes  serrated  spines, 
which  are  used  as  weapons  of  offence. 


Sharks. 


FIG.  12. 


The  heart  in  sharks  has  a  long  arterial  cone.  The 
intestine,  though  short,  is  very  capacious,  and  has  the 
extent  of  its  inner  surface  in- 
creased enormously  by  means 
of  a  long  spiral  fold  of  its 
lining  mucous  membrane, 
which  stretches  throughout 
almost  its  whole  extent.  Like 
the  lampreys,  sharks  are  de- 
void of  a  swimming-bladder. 

Some  sharks  are  vivipa- 
rous (that  is,  produce  their 
young  alive) ;  in  others  the 
young  are  extruded  within 
curious  horny  tendril-bearing 
rases,  which  are  often  picked 
up  along  the  sea-shore,  and 
are  commonly  called  '  mer- 
maids' purses.' 

The  commonest  examples 
of  this  order  are  the  dog-fishes, 
sharks,  and  rays.  One  of  the 
largest  forms  is  the  great  bask- 
ing shark  of  the  North  At- 
lantic ;  this  fish  is  not  at  all 
uncommon  on  the  west  coast 
of  Ireland,  where  it  is  called 
the  sun-fish,  and  is  often  cap- 
tured for  its  oil.  It  also  oc- 
curs, though  but  rarely,  on  the 
American  coast.  It  often  ex- 
ceeds thirty  feet  in  length,  and  a  specimen  of  this 
size  will  yield  ninety  gallons  of  oil  from  its  liver.  The 


Beak  of  saw-fish  seen  from  Le- 
low,    showing    its    mout 
nostrils,  and  lateral  teeth. 


26  Vertebsata. 

gigantic  Rhinodon  of  the  Indian  Ocean  has  been  met 
with  sixty  feet  in  length.  The  hammer-headed  shark, 
with  its  extraordinary  bilobed  head,  and  the  saw-fish 
(fig.  12),  with  its  long,  flattened,  bony  snout  bearing  a 
row  of  strong,  sharp  teeth  on  each  side,  are  also  ex- 
amples of  the  order. 

The  skates,  or  rays,  are  remarkable  for  their  flat- 
tened form,  due  largely  to  the  enormous  size  of  the 
pectoral  fins.  One  form,  rarely  found  in  British  seas, 
though  common  in  the  Mediterranean,  is  the  torpedo 
or  electric  ray,  which  has  near  its  head  two  large 
electric  batteries,  whereby  the  fish  can  give  severe 
electric  shocks;  these  organs  are  joined  to  the  brain 
by  large  nerves,  and  consist  of  closely  apposed 
columnar  elements,  which  morphologically  are  con- 
sidered to  consist  of  extremely  modified  muscular 
tissue. 


CHAPTER  V. 

ORDER   3,   GANOID    FISHES  ;    ORDER   4,   BONY   FISHES  ; 
ORDER    5,  DIPNOI. 

16.  Order  3,  Ganoidei. — The  living  fishes  of  this 
group  are  very  few  (about  thirty),  and  most  of  them 
are  inhabitants  of  rivers  or  of  lakes  but  in  former 
times  they  were  apparently  numerous  and  rich  in 
species,  as  the  fossil  remains  of  six  hundred  species 
are  already  known.  They  are  characterised  by  pos- 
sessing ganoid  scales — that  is,  brightly  polished  plates 


Bony  Fishes.  27 

covered  with  a  lamina  of  an  enamel-like  substance. 
They  have  likewise  unsymmetrical  tails  and  a  ventri- 
cular arterial  cone.  The  gills  are  free,  and  are  placed 
on  bony  gill-arches,  under  cover  of  opercula  or  gill- 
flaps,  not  in  pouches  nor  on  plates.  Some,  like  the 
sturgeons,  have  a  persistent  notochord  ;  others,  like 
the  Californian  bony  pike,  have  fully  ossified  verte- 
bral bodies.  The  other  forms  included  in  this  order 
are  the  Polypterus  of  the  Nile  and  the  reed  fish  of 
Calabar,  as  well  as  several  rare  and  curious  American 
species.  Many  of  the  fossil  forms  were  of  large  size 
and  of  extraordinary  shapes  ;  their  remains  abound 
in  some  of  the  old  red  sandstone  formations.  All 
living  forms  have  a  swimming-bladder,  which  in  the 
sturgeon  yields  the  isinglass !  of  commerce. 

1 7.  Order  4,  Teleostei.—  This  is  by  far  the  largest 
group  of  fishes,  and  includes  all  those  which,  like  our 
common  fishes,  possess  a  bony  skeleton  with  bicon- 
cave vertebral  bodies.  The  tail  consists  of  two  even 
lobes  supported  on  a  sharply  upturned  and  conti- 
nuously ossified  end  of  the  vertebral  column  (fig.  6). 
The  body  has  usually  a  uniform  coating  of  smooth  or 
ribbed  or  spinose  scales,  which  rarely  have  an 
enamelled  surface.  The  gills  consist  of  free,  usually 
comblike,  filaments  on  bony  branchial  arches  (fig.  10), 
arranged  under  the  flaplike  gill-cover  or  operculum. 
There  is  no  arterial  cone,  the  mouth  of  the  ventricle 
having  but  one  row  of  valves. 

This  order  of  fishes  is  divided  into  the  following 
six  sub-orders  : — 

1  Isinglass  is  a  corruption  of  the  German  ffausenblase,  from 
ffauscn,  a  sturgeon,and  Blase,  a  bladder— i.e.  sturgeon's  bladder. 


28  Vertebrata. 

SUB-ORDER  i,  PHYSOSTOMI,  or  those  in  which  the 
swimming-bladder  communicates,  in  the  adult,  with 
the  digestive  canal  by  means  of  a  duct.  In  these 
also  all  the  fin  rays  are  soft  and  jointed,  except 
perhaps  the  foremost  ray  of  each  fin,  which  may  be 
spinose  from  a  fusion  of  its  separate  elements.  In 
this  group  are  included  the  pike,  carp,  goldfish, 
herring,  salmon,  trout,  and  most  of  our  fresh-water 

FIG.  13. 


d, 

Viscera  of  herring. 

s  ;  b,  c,  stomach,  with  its  appendages,  d ;  e,  intestine  ; 
',  duct  of  the  swimming-bladder,  k  ;  h,  ovary. 

fishes,  such  as  the  barbel,  tench,  roach,  ide,  minnow, 
&c.  Some  of  these  physostome  fishes  have  no 
ventral  fins — for  example,  the  eels,  a  few  of  which,  like 
the  prettily  marked  Helen's  eel  of  the  Mediterranean, 
are  also  devoid  of  pectoral  fins.  One  genus  of  eels, 
the  Gymnotus,  of  the  large  rivers  of  South  America, 
has  a  powerful  electric  organ,  formed  of  some  of  the 
modified  body  muscles.  This  apparatus  stretches 
along  almost  the  entire  body,  and  as  the  fish  some- 
times reaches  the  length  of  six  feet,  the  organ  is  of 
very  considerable  size,  and  is  capable  of  giving  violent 
electric  shocks.  Two  other  genera  of  physostome 


Flat  Fishes.  29 

fishes  have  also  electric  organs ;  one  of  these  is  a 
genus  of  river  h^s—Malapterurus,  from  the  Nile — 
the  other— Mormyrus,  also  African — has  a  very  small 
electric  organ  near  the  tail. 

Some  fishes  belonging  to  a  curious  marine  group 
of  this  sub-order— the  Scopelidae — are  remarkable  not 
only  for  the  brilliancy  of  their  lustre,  but  for  the  fact 
of  their  possessing  several  pairs  of  accessory  eyes  on 
the  gill  covers.  One  other  species  of  physostome  fish — 
Amblyopsis  which  inhabits  the  Mammoth  Cave  of 
Kentucky — is  remarkable  for  the  rudimentary  condition 
of  its  eyes,  which  are  covered  with  a  layer  of  skin, 
and  are  hence  functionless. 

SUB-ORDER  2,  ANACANTHINI. — This  subdivision 
includes  those  soft-finned  fishes  which  have  either  no 
swimming-bladder  or  have  one  that  has  no  duct.  In 
these  not  even  the  foremost  fin-rays  are  spinous,  but 
all  are  soft-jointed  and  branched.  They  are  for  the 
most  part  marine,  and  include  many  of  the  common- 
est of  our  sea  fishes,  such  as  the  cod,  haddock, 
whiting,  saith,  lithe,  ling,  &c.  One  interesting  group 
— that  of  the  flat  fishes — is  remarkable  for  the  want 
of  symmetry  displayed  in  the  body,  which  is  ex- 
tremely compressed,  and  the  animal  in  progression 
invariably  lies  on  one  side,  swimming  with  one  side 
up  and  the  other  directed  downwards.  These  fishes 
usually  keep  near  or  on  the  bottom,  and  the  upper 
side  is  usually  dark  or  coloured  while  the  lower  side 
is  white.  To  accommodate  the  structures  of  the 
animal  to  this  extraordinary  habit,  the  eyes  are  twisted 
round  both  to  the  one  side  of  the  head — viz.  that 
which  is  uppermost — so  are  the  nostrils,  and  the 


30  Vertebrate 

mouth  is  also  usually  awry,  so  as  to  give  the  greatest 
amount  of  facility  of  swallowing  consistent  with 
position.  As  in  this  distorted  position  the  dorsal 
and  anal  fins  are  disposed  as  lateral  fringes,  they 
functionally  replace  the  paired  fins  as  directors  of 
motion,  and  hence  the  pectoral  and  ventral  fins  are 
usually  small  or  deficient.  One  interesting  feature  in 
these  fishes  is  that  their  embryos  at  a  very  early  stage 
are  perfectly  symmetrical,  and  gradually  develope  the 
one-sided  torsion  as  growth  progresses,  the  displaced 
eye  having  been  traced  by  observers  in  its  curious 
pilgrimage  around  the  front  of  the  obliquely  growing 
head  from  the  under  to  the  upper  side.  The  turbot, 
plaice,  flounder,  sole,  dab,  and  fluke  are  well-known 
examples  ;  the  largest  species  inhabiting  our  seas  is 
the  halibut,  which  sometimes  has  been  known  to 
attain  the  weight  of  over  500  pounds.  Another 
curious  point  is  noteworthy— viz.  that  though  in  each 
genus  the  side  to  which  the  eyes  are  displaced  is 
usually  constant,  yet  erratic  reversed  examples  are 
occasionally  met  with.  Thus  while  in  the  flounder 
and  plaice  the  eyes  are  usually  on  the  right,  in  such 
reversed  cases  they  are  found  looking  to  the  left ; 
such  abnormalities  are  easily  understood  by  the  light 
of  the  embryonic  development  of  the  group. 

One  genus  of  fish  of  this  sub-order,  named 
Fierasfer,  is  parasitic  within  the  bodies  of  certain 
sea-cucumbers,  or  holothurians,  and  star-fishes,  and 
is  found  in  the  Indian  Ocean. 

SUB -ORDER  3,  ACANTHOPTERI.  —  Spiny -finned 
fishes  with  a  ductless  swimming-bladder,  or  else  none. 
This  is  the  most  numerous  and  most  specialised  group 


Spiny-finned  Fishes,  3 1 

of  bony  fishes.  The  scale-clothing  of  this  class  is 
usually  remarkable  for  the  comblike  or  spiny  surface 
and  hinder  margin  of  each  scale,  whereby  they  are 
distinguished  from  the  circular  smooth  scales  of  the 
ph>  sostome  fishes.  The  most  familiar  examples  are 
the  perches  of  our  streams ;  the  bull-heads  and  gur- 
nards, known  by  their  spiny  heads,  found  along  our 
coasts  ;  the  sticklebacks,  so  interesting  on  account  of 
the  nests  constructed  by  the  males  for  the  protection 
of  the  young  :  the  mullets,  which  have  the  singular 
property  of  changing  colour  when  they  are  dying  ;  the 
mackerels,  bi  earns,  braizes,  blennies,  gobies,  &c. 

Some  of  these  fishes  are  laterally  compressed,  like 
flat  fish,  but  without  showing  any  distortion  of  the 
heads,  such  as  the  John  d;Ory  and  Archer  fishes  ;  the 
latter  are  East  Indian  fishes,  and  owe  their  name  to 
their  habit  of  shooting  at  flies  by  forcibly  ejecting 
drops  of  water  from  their  long  snouts.  The  sword- 
fish,  which  sometimes  attains  the  length  of  sixteen  feet, 
is  closely  allied  to  the  mackerel,  and  is  remarkable  for 
the  long,  swordlike  upper  jaw.  The  common  lump- 
sucker,  the  little  red  or  brown  Lepadogaster  of  En- 
gland, and  the  tropical  Remora  are  remarkable  as 
being  provided  with  sucking  disks,  whereby  they  can 
adhere  with  great  tenacity  to  foreign  bodies.  Fistularia 
(the  tobacco-pipe  fish)  is  remarkable  for  his  long 
tubular  snout,  as  is  also  the  allied  trumpet- fish. 
Trachinus  (the  weever)  is  said  to  be  able  to  inflict 
poisonous  wounds. 

There  are  three  aberrant  groups  of  spiny-fmned 
fishes,  which  constitute  the  remaining  three  sub-orders. 

The  first  of  these,  or  sub-order  4,  is  called  Pharyn 


32  Vertebrata. 

gognathi,  or  pharynx-jaw-bearing  fishes,  on  account  of 
the  presence  of  a  single  medial  tooth-bearing  bone  in 
the  pharynx,  made  up  of  the  united  lateral  remains  of 
one  of  the  hindmost  of  the  visceral  arches,  which  does 
not  bear  gills.  The  flying  fishes,  distinguished  by 
their  long  pectoral  fins  ;  the  gar-pikes  and  parrot 
fishes  ;  the  cunners  and  tautogs,  so  common  along 
our  shores,  are  the  most  familiar  examples  of  the 
group.  They  are  small  or  moderate-sized  hshes,  with 
spiny  fins,  and  often  with  strong  conical  teeth  in  the 
jaws. 

Sub-order  5  consists  of  the  sea  horses  and  pipe 
fishes,  which  differ  from  all  other  fishes  in  having  the 
gill  filaments  in  symmetrical  clusters  or  tufts  on  the 
gill  arches,  not  in  comblike  plates  ;  hence  they  are 
called  Lophobranchii,  or  tufted-gilled  fishes.  Their 
bodies  are  clad  with  bony  plates,  and  are  often  of 
eccentric  angular  shapes.  They  have  no  ribs,  their 
jaws  are  toothless,  and  the  males  in  some  species 
are  provided  with  pouches  on  the  front  of  the 
abdomen,  into  which  they  collect  the  eggs  on  their 
being  laid  by  the  females,  and  within  which  the 
young  are  hatched. 

The  sixth  sub-order,  PUctognathi,  or  soldered  jaws, 
consists  of  spiny-finned  fishes  in  which  the  bones  of 
the  upper  jaw  are  consolidated  together  instead  of 
remaining  separate ;  these  are  the  singular  globe-fishes, 
whose  spiny  bodies  are  capable  of  inflation,  and  whose 
bare,  ivory-like  teeth  give  them  such  a  remarkable 
appearance.  The  file  fishes  also,  with  their  rough, 
branched  spines  and  tough  skin  and  the  angular  box- 
fishes,  which  belong  to  this  order,  are  likewise  among 


Mud  Fishes. 


33 


the  most  singularly  shaped  of 
tropical  fishes.  One  remarkable 
species — the  sun  fish — a  large 
globular  fish  with  an  extraordi- 
narily thick  skin,  sometimes 
reaches  the  weight  of  400 
pounds. 

1 8.  Order  5,  Dipnoi.-  This, 
the  last  and  in  some  respects 
most  interesting  order,  includes 
three  living  fishes,  which  form 
a  transition  to  the  next  class. 
These  fishes  differ  from  all  the 
foregoing  in  having  the  swim- 
ming-bladder developed  as  an 
accessory  respiratory  organ  ;  the 
blood  returning  from  it  being 
received  into  a  small  additional 
auricle  of  the  heart  placed  to 
the  left  of  the  main  auricle. 
They  have  a  covering  of  horny 
scales,  and  the  alimentary  canal 
has  a  spiral  valve.  They  also 
exhibit  the  peculiarity  of  pos- 
sessing tubular  nasal  passages 
which  perforate  the  upper  lip, 
opening  into  the  mouth.  One 
of  the  fishes  of  this  order  is  the 
African  mud  fish,  or  Protopterus 
of  the  Gambia ;  another  is  the 
Lepidosiren  (fig.  14),  of  South 
America  ;  and  the  third  is  the  (The  mud  fish 

D 


34  Vertebrata. 

Ceratodus,  of  the  rivers  of  Queensland.  In  several 
respects  these  fishes  present  characteristics  which  are 
identical  with  the  embryonic  conditions  of  many  of 
the  higher  groups  of  animals.  The  characters  of  the 
skeleton  can  be  seen  in  fig.  7. 


CHAPTER  VI. 

CLASS    2,   AMPHIBIA. 

19.  Characters  of  Amphibia.^-The  class  Am- 
phibia, to  which  we  are  structurally  conducted  by  the 
last  order  of  fishes,  consists  of  cold-blooded  animals, 
usually  of  small  size.  This  is  at  present  the  poorest 
in  species  of  all  the  classes  of  vertebrata,  yet,  as  in  the 
case  of  the  ganoid  fishes,  at  earlier  periods  in  the 
world's  history  the  animals  of  this  class  vastly  ex- 
ceeded their  present  representatives  in  number,  size, 
and  complexity.  Like  fishes,  they  are  characterised 
by  having  a  feeble  development  of  the  outer  skin, 
or  epidermis,  but,  unlike  them,  they  have  no  dermal 
clothing  of  scales,  and  the  surface  is  generally  smooth, 
naked,  and  often  glandular.  Some  of  them,  in  the 
embryonic  or  tadpole  stage  of  their  existence,  possess 
rudiments  of  the  system  of  sense  organs,  like  those 
of  the  lateral  line  in  fishes,  but  none  of  them  are 
retained  in  the  adult  state.  Amphibians,  moreover, 
have  no  functional  fin-rays,  though  sometimes  they 
have  marginal  membranous  fringes,  as  in  the  common 
newt  or  tadpole,  and  even  rudimentary  rays,  as  in  the 


Characters  of  A  mphibians.  3  5 

toe-webs  of  some  salamanders.  They  also  undergo 
regular  metamorphoses,  beginning  life  as  little  fish- 
like  creatures  with  large  flat  heads  and  external  gills. 
To  this  stage  the  name  tadpole  is  commonly  given. 
Then,  as  development  progresses,  the  air  sacs  (which 
correspond  to  the  swimming-bladder  in  fishes)  grow, 
become  large,  vascular,  and  capable  of  acting  as 

FIG.  15. 


Skeleton  of  frog. 

«*,  skull ;  b,  vertebrae  ;  c.  sacrum ;  d,  ilium ;  e,  urostyle  ;  /,  suprascapula  ; 
g,  humerus  ;  h,  fore-arm  bones  ;  «',  wrist  bunes ;  m,  thigh  bone  ;  n,  leg 
bones  ;  o,  elongated  first  pair  of  ankle  bones  ;  /,  q,  foot  bones. 

breathing  organs,  which  are  then  called  lungs ;  and 
ultimately,  in  the  adult  state,  a  pulmonary  or  direct 
air-breathing  system  supplants  the  gill  or  branchial 
system  of  earlier  life.  The  two-chambered  larval 
heart  at  the  same  time  becomes  three-chambered, 
developing  a  special  auricle  in  the  left  side  for  the 
reception  of  the  blood  which  has  been  purified  in 

D  2 


36  Vertebrata. 

the  lungs,  and  is  returned  from  hence  into  the  heart. 
It  may  also  be  noted  that,  during  this  process  of 
development  in  the  common  frog  the  digestive  canal, 
which  in  the  tadpole  is  long  and  spirally  coiled, 
becomes  shorter  and  straighter  The  blood  of  amphi- 
bians is  remarkable  for  the  large  size  of  the  oval  red 
corpuscles  which  it  contains,  those  in  Proteus  being 
of  an  inch  in  diameter,  those  in  the  frog  being 
The  vertebral  column  in  the  simplest  of  the 
amphibians  consists  of  rudimentary  or  biconcave 
vertebrae  ;  in  frogs  (fig.  15),  however,  it  consists  of  a 
chain  of  a  few  solid  disks  whose  surfaces  fit  into  each 
other  by  ball  and  socket  joints.  Ribs  are  either  very 
short  or,  as  in  frogs,  absent.  The  skull  articulates 
to  the  foremost  vertebra  by  means  of  two  lateral  arti- 
cular surfaces  which  are  called  condyles.  The  skull 
12  also,  as  a  rule,  much  more  consolidated  than  the 
skull  in  fishes,  but  resembles  the  latter  in  having,  as 
the  most  conspicuous  bone  in  its  base,  a  long  ossifi- 
cation in  the  membrane  underlying  the  middle  of  the 
cartilage  of  the  base  of  the  skull,  which  is  known  as 
the  parasphenoid  bone,  a  bone  which  is  rudimental  or 
absent  in  all  higher  forms.  Amphibians  also  differ 
from  fishes  in  having  a  middle  ear,  closed  by  a  tym- 
panic membrane,  and  not  merely  the  internal  ear 
cavity  which  constitutes  the  ear  in  fishes.  Their  nasal 
cavities  open  posteriorly  into  the  pharynx.  They 
have  usually  four  limbs,  which  consist  of  parts  com- 
parable with  those  in  higher  animals,  and  very  unlike 
the  fins  in  fishes. 

There  are  three  orders  of  amphibians  at  present 
represented  by  living  forms  on  the  globe. 


37 
CHAPTER  VII. 

CLASSIFICATION    OF   AMPHIBIA. 

20.  Order  1,  Gymnophiona. — A  small  group  of 
worm-like  forms,  with  no  limbs,  rudimental  eyes 
(hence  they  are  called  C(Kcilia\  which  are  found  in 
tropical  countries  burrowing  in  the  ground.  These, 
with  one  exception,  have  the  body  provided  with 
dermal  scales.  They  are  usually  marked  with  super- 
ficial rings  like  an  earth-worm,  and  range  in  size  from 
one  to  two  feet,  rarely  exceeding  this  length.  At 
present  only  a  few  species  exist,  but  many  fossil  forms 
have  been  found  which  probably  resembled  these  in 
structure. 

A  large  and  structurally  complex  order  of  fossil 
amphibians,  named  Labyrinthodonts,  formerly  in- 
habited the  earth,  which  in  some  respects  seem  to 
have  been  related  to  the  Ccecilians,  but  were  much 
larger,  and  many  of  them  were  defended  by  dermal 
coats  of  bony  mail  something  like  the  armour  clothing 
of  a  crocodile. 

2 1  Order  2,  TIrodela. — Limb-bearing  amphibians 
provided  with  a  permanent  tail,  which  is  retained 
during  life.  There  are  two  sections  in  this  order,  in 
one  of  which  the  animals  retain  their  embryonic  gills 
through  their  whole  existence,  and  are  thus  peren- 
nially or  permanently  branchiate,  while  in  their  adult 
condition  they  also  possess  lungs,  which  become  de- 
veloped gradually  in  process  of  growth.  In  the  other 
section  the  gills  are  only  transitory  or  caducous, 


Vertebrata. 


FIG. 


wasting  and  disappearing  on  the  development  of  the 
lungs.  Of  the  former,  we perennibranchiate  section  we 
have  interesting  examples  in  the  sirens  or  mud  .eels  of 

Carolina,  which  are 
provided  with  only 
two  limbs  represent- 
ing the  fore  limbs 
of  other  verte- 
brates. Another 
form,  the  proteus, 
inhabits  the  Cave 
of  Adelsberg  and 
other  caves  in  Ca- 
rinthia,  &c.,  and  is, 
like  all  other  cave- 
dwellers,  blind  and 
blanched ;  its  weak 
fore  legs  are  pro- 
vided with  three 
toes,  while  the  hind 
limbs  possess  only 
two.  The  curious 
axolotl  (fig.  1 6)  of 
Mexico  is  an  inte- 
resting form,  as  it 
has  proved  to  be  a 
permanent  tadpole 
which  in  certain 
conditions  only  un- 
dergoes its  further  metamorphosis  into  the  salamander- 
like  form  of  its  adult  state. 

Jn  some  perennibranchs  the  outer  gills  disappear, 


Diagram  of  the  axolotl,  showing  its  gills,  6, 
and  lungs,  v. 


Frogs.  39 

and  are  replaced  by  an  internal  series,  or  gills  of  the 
type  of  those  developed  in  fishes.  This  modification 
in  the  structure  of  these  organs  is  of  considerable  inte- 
rest from  a  morphological  point  of  view,  when  we  re- 
member that  in  sharks  there  are  originally  in  the 
embryo  distinct  external  gills,  which  are  lost  as  the 
shark  attains  his  more  perfect  organisation,  and  are 
replaced  by  the  permanent  gills,  which  are  formed 
directly  on  the  aortic  arches.  From  these  conditions 
it  seems  as  if  external  gills  were  a  more  primitive  or 
embryonic  form,  and  internal  gills  a  more  specialised 
modification  of  respiratory  organs.  The  amphibians 
which  show  these  internal  gills  are  the  giant  Sieboldia 
of  Japan,  which  reaches  a  length  of  four  feet,  and  the 
amphiuma  and  menopoma  of  North  America.  The 
caducibranchiate  tailed  amphibians  are  the  sala- 
manders and  newts,  the  latter  of  which  are  common 
in  our  ditches,  where  their  metamorphoses  ^an  easily 
be  traced.  The  common  newt  is  interesting  on  ac- 
count of  the  bright  colours  which  it  exhibits  at  certain 
stages,  and  for  the  remarkable  dorsal  crest  which  it 
also  occasionally  possesses. 

22.  Order  3,  Annra.— The  largest  group  of  the 
Amphibia  consist  of  the  frogs  and  toads,  or  the  tailless 
forms.  In  these,  the  larva  or  tadpole  loses  during 
its  development  all  traces  not  only  of  its  gills,  but  also 
of  its  tail ;  the  hinder  limbs  are  also  in  these  more 
perfectly  developed  than  the  fore,  and  the  two  proxi- 
mal bones  of  the  ankle  are  elongated,  so  as  to  make 
what  appears  to  be  an  independent  third  portion  of 
the  hind  limb.  The  fore  arm  and  the  leg  proper  also 
differ  from  those  of  urodeles  and  of  the  higher  verte- 


4O  Verlebrata. 

brates  in  that  there  are  only  single  bones  in  these 
regions,  the  separate  bones,  radius  and  ulna,  which 
are  present  in  these  parts  of  other  vertebrates  being 
here  united.  The  frogs,  toads,  pipas,  and  tree  frogs 
are  the  most  striking  examples  of  this  order. 


CHAPTER  VIII. 

CLASS    3,    REPTILES. 

23.  Characters  of  Reptilia. — Tortoises,  lizards, 
snakes,  and  crocodiles  are  the  leading  forms  included 
in  this  large  third  class  of  vertebrate  animals,  a  class 
often  confounded  with  the  amphibians,  but  differing 
therefrom  in  many  striking  and  characteristic  respects. 
Reptiles  are  invariably  provided  with  a  very  distinct 
epidermic  clothing  of  scales  which  differ  essentially 
from  the  dermal  scales  of  the  foregoing  groups.  The 
scales  of  reptiles  being  epidermal,  and  not  parts  of  the 
derm  is  or  true  skin,  are  often  shed  and  replaced,  as 
in  snakes,  and  they  are  sometimes  hard  and  thick,  as 
in  the  tortoise  shell  of  commerce  and  in  the  mail 
clothing  of  the  crocodile.  This  firm  covering  may  be 
supplemented  by  a  dermal  bony  layer,  as  in  croco- 
diles or  tortoises,  but  these  indurations  of  the  dermis 
are  never  superficial.  The  blood  is  cold  ;  the  aortic 
arches  never  bear  gills,  nor  is  there  ever  branchial 
respiration  in  any  stage  of  existence  among  the  animals 
of  this  group.  The  heart  consists  of  three  cavities, 
two  auricles  and  one  ventricle  j  but  the  latter  is  often 


CJiaracters  of  Reptiles. 


FIG.  17. 


more  or  less  perfectly  divided  by  a  septum,  so  as  to 
act  as  if  it  were  a  double  chamber  (fig.  17).  There  are 
always  at  least  two  aortic  arches,  right  and  left,  which 
usually  unite  sub  vertebral  ly  to  form  one  dorsal  aorta. 
The  notochord  never  per- 
sists in  the  adult,  and  in 
most  living  reptiles  the 
vertebral  bodies  unite  witn 
each  other  by  ball  and 
socket  joints,  and  are  very 
rarely  biconcave.  The 
skull  joins  the  vertebral 
column  by  a  single  me- 
dian articular  eminence 
or  condyle,  and  there  is 
no  parasphenoid  bone, 
the  bones  of  the  middle 
of  the  base  of  the  skull 
being  developed  in  the 
cartilage  of  the  base  itself, 
not  in  the  membrane  be- 
neath the  cartilage.  The 
lower  jaw  articulates,  as 
in  the  amphibians,  with 
the  end  of  the  preceding  visceral  arch  ;  and  a  bone 
at  its  extremity  called  the  quadrate  bone  is  interposed 
between  the  palatine  part  of  that  arch  and  the  skull. 

Many  reptiles  are  ovoviviparous ;  others  are  ovi- 
parous. Like  the  amphibians,  the  reptiles  at  the  present 
day,  though  still  numerous,  give  us  a  very  faint  idea  of 
their  former  grandeur  of  size  and  complexity.  In  the 
Mesozoic  age  they  held  the  same  position  on  the  globe 


Heart  of  turtle. 
H,  ventricle  ;  h,  h1 .  auricles. 


42  Vertebrata. 

that  the  Mammalia  do  at  the  present  period.  Only 
four  orders  of  reptiles  are  represented  in  the  existing 
terrestrial  fauna ;  at  least  five  orders,  and  these  in- 
cluding the  giants  of  the  class,  have  perished. 


CHAPTER  IX. 

LIZARDS   AND    SNAKES. 

24.  Order  1,  Lacertilia.— The  lizards  are  scale- 
clad,  and  at  least  forelimb-bearing  reptiles,  with  a  heart 
possessing  a  single  ventricle,  and  with  a  lower  jaw  of 
firmly  united  segments.  The  eyes  are  provided  with 
movable  and  functional  eyelids,  and  the  teeth  are  not 
in  sockets,  but  are  disposed  in  rows  either  around 
the  edge  or  along  the  side  of  the  jaws. 

The  cloaca,  or  cavity  into  which  the  digestive 
canal  and  excreting  orifices  open,  has  usually  its 
outlet  placed  transversely.  Like  most  of  the  lowly 
organised  vertebrates,  lizards  display  a  remarkable 
power  in  restoring  lost  parts,  and  in  connection  with 
this  we  perceive  in  them  a  facility  for  making  their 
escape  from  capture  by  breaking  off  their  extremities. 
Thus  a  lizard  taken  by  the  tail  will  often  break  off 
that  process  and  escape,  the  fracture  taking  place 
not  between  two  of  the  vertebrae  which  make  up  the 
organ,  but  actually  through  the  middle  of  a  vertebra, 
as  there  is  a  medial  cartilaginous  plate  in  the  caudal 
vertebrae  of  some.  In  one  specimen  in  the  writer's 
possession  a  lizard  whose  tail  was  cracked,  but  not 


Lizards.  43 

broken  off,  developed  at  the  crack  an  accessory  tail, 
while  the  original  tail  yet  remained  and  became  re- 
paired at  its  injured  part,  thus  giving  a  bifid  extremity 
to  the  tail. 

Some  lizards  are  snakelike  and  ringed,  like  the 
amphisbaenas,  with  no  projecting  limb-rays,  but  in  all 
these  traces  of  the  limb  girdles  are  persistent,  although 
they  may  not  show  superficially,  as  in  the  blind  worm — 
a  pretty  and  innocent,  though  much  maligned,  native 
of  Great  Britain,  whose  scientific  name  Anguis  fragilis, 
expresses  the  brittleness  before  referred  to.  The 
common  wall-lizards  are  typical  examples  of  the  long 
fork-tongued  division  of  the  order.  The  monitors 
and  teguexins,  or  safeguards  of  the  tropics,  are  so  called 
because  they  are  supposed  to  give  warning  of  the 
presence  of  crocodiles.  They  reach  the  length  of  six 
to  eight  feet,  and  are  among  the  largest  of  living 
lizards,  although  they  are  but  pigmies  when  compared 
with  the  extinct  forms  of  which  fossil  remains  have 
been  found,  sometimes  exceeding  thirty  feet  in  length. 

The  American  iguanas  are  large-sized  lizards 
which  are  used  as  food ;  they  usually  bear  tufted 
crests  on  the  back,  and  have  thick  short  tongues. 
Some  lizards  have  large  lateral  flaps  of  skin  :  thus  the 
frilled  lizard  of  Australia  bears  on  each  side  of  the 
neck  a  wide  fold  of  skin  like  a  ruff  or  Queen  Eliza- 
beth collar ;  others,  like  the  little  flying  dragon,  bear 
on  each  side  a  winglike  fold,  supported  on  extended 
ribs,  and  these,  together  with  the  long  conical  chin- 
pouch,  give  this  creature  a  very  extraordinary  appear- 
ance. The  appropriately  named  Moloch  Jwrridus  of 
Australia  bristles  most  repulsively  with  conical  spines, 


44 


Vertebrata. 


as  do  many  other  genera.  The  geckos  of  India  are 
remarkable  for  the  suckers  which  they  bear  on  the 
ends  of  their  fingers,  whereby  they  can  walk  up  per- 
pendicular walls  and  along  ceilings.  The  last  group  of 
lizards,  the  chameleons,  are  interesting  for  their 
proverbial  quality  of  changing  colour,  due  to  the  ex- 
pansion and  contraction  of  certain  pigment-bearing 
connective  tissue  bodies  in  the  skin.  They  also 

FIG.  18. 


Head  of  chameleon,  with  protruded  tongue. 

possess  circular  eyelids,  and  a  very  long  tongue  (tig. 
1 8)  capable  of  being  protruded  with  lightning-like 
rapidity. 

25,  Order  2,  Ophidia  (Snakes). — These  dreaded 
animals  may  be  regarded  in  some  respects  as  special 
modifications  of  the  lizard  type.  They  are  scale-clad 
and  limbless,  not  having  even  a  remnant  of  the 
shoulder  girdle  persistent.  The  sternum  and  sternal 
apparatus  have  also  vanished,  and  the  skeleton  consists 
of  a  long  vertebral  column,  often  of  several  hundred 
joints  or  vertebrae,  each  of  which  bears  two  ribs,  one 
on  each  side. 


Serpents.  45 

The  vertebrae  have  each  a  concavity  on  the 
anterior  side  of  each  body,  into  which  the  ball  or 
convexity  of  the  hinder  surface  of  the  foregoing  body 
fits.  There  are  also  two  pairs  of  articular  facets  on 
the  processes  of  each  vertebra,  so  that  the  entire 
spine  combines  flexibility  with  amazing  strength. 
The  ribs  are  capable  of  being  moved  forwards  and 
backwards,  and  the  ventral  surface  of  the  animal's 
body  is  covered  with  flat,  horny  shields,  into  which 
muscles  run  from  the  tip  of  each  rib.  The  rapid, 
even,  gliding  motion  in  serpents  is  accomplished  by 
the  successive  advances  of  these  ventral  scutes,  and 
the  drawing  of  the  body  forwards  towards  them,  while 
the  slightly  projecting  hinder  edges  of  the  scutes 
serve  as  fixed  points  by  catching  the  surface  of  the 
ground.  The  brain  case  is  firmly  built  up  of  sin- 
gularly united  bones ;  but  the  bones  of  the  upper  and 
lower  jaw-arches  are  loose,  united  together  by  means 
of  fibrous  tissue,  and  hence  capable  of  an  extreme 
degree  of  stretching  during  the  swallowing  of  food, 
which  these  animals  bolt  in  large  masses. 

The  teeth  are  recurved  and  solidified  to  the  jaw, 
not  set  in  sockets,  and  they  can  only  act  as  organs  of 
prehension. 

The  tongue  consists  of  a  long,  bifid  muscular  organ, 
capable  of  being  rapidly  protruded,  or  of  being  drawn 
back  into  a  sheath  when  not  in  use.  The  windpipe 
is  long  and  protected  by  complete  gristly  rings ;  only 
one  lung  is  usually  large  and  developed,  the  other  is 
rudimental  or  simply  saccular,  and  they  are  never 
symmetrical.  The  digestive  canal  is  capacious  and 
short,  and  the  cloacal  opening  is  transverse.  The 


46 


Vertebrata. 


eyelids  are  confluent  and  transparent,  forming  the 
clear  glassy  surface  of  the  eye,  and  thus  giving  to  the 
serpent  the  stony,  unwinking  stare  peculiar  to  them. 

The  boas  of  the  New  World,  and  pythons  of  the 
East,  are  remarkable  among  snakes  for  their  size  and 
for  the  strength  of  their  teeth,  as  well  as  for  the  pos- 
session of  two  rudimentary  hind  limbs  in  the  form  of 
spur-like  processes  placed  one  on  each  side  of  the 
cloaca.  Some  of  these  serpents,  like  the  anaconda  of 

FIG.  19. 


Poison  fangs  showing  their  internal  hollows. 

America,  have  been  known  to  reach  the  length  of 
forty  feet,  and  even  larger  specimens  are  described. 

The  Colubrine  snakes,  such  as  the  common  Amer- 
ican striped  snake  (Eutcemia  sertalis),  are  all  harmless 
creatures,  mostly  of  small  size,  and  having  all  the 
teeth  solid,  not  grooved. 


Poison  Fangs  of  the    Viper. 


47 


26.  Poisonous  Snakes.  —  The  most  remarkable, 
though  not  the  most  numerous  group  of  serpents, 
are  those  provided  with  poison-fangs,  the  vipers  and 
rattlesnakes.  Of  these  the  best  known  is  the  rattle- 
snake, in  which  animal  the  epidermal  clothing  of  the 
last  few  tail-joints  is  loose,  and  consists  of  hard,  horny 
rings  loosely  embracing  each  other  ;  these  cause  the 
rattling  noise,  when  the  animal's  tail  is  shaken,  which 
nas  given  rise  to  the  name  of  this  dreaded  American 
snake.  Like  most  other  poisonous  snakes,  it  has 


FIG. 


Poison  apparatus  of  rattlesnake. 
a,  poison  bag  and  duct ;  e,  i,  g,  t,  v,  muscles  of  jaw. 

a  flat  triangular  head,  and  in  its  mouth  there  can  be 
seen  the  two  long  grooved  maxillary  teeth  in  which 
are  the  channels  for  the  poison.  These  are  the  only 
large  teeth  in  the  mouth,  all  the  others  being  small 
and  obscure.  They  are  placed  far  forwards  in  the 
upper  jaw,  and  are  movable  along  with  the  movable 
maxilla,  being  bent  upwards  towards  the  palate  in  the 


48  Vertebrata. 

closed  position  of  the  mouth,while  in  the  gaping  state 
they  project,  being  arched  downwards,  ready  to  be 
inserted  into  the  victim  about  to  be  struck.  The 
groove  in  the  tooth  leads  into  a  canal  which  traverses 
the  base  of  the  poison  fang,  and  is  continued  by  a 
duct  into  a  cavity  or  sac,  which  receives  the  tubular 
ducts  of  the  poison  gland  (fig.  20).  In  the  act  of 
striking,  the  muscles  which  close  the  jaws  squeeze  the 
poison  sac  and  drive  the  poison  through  the  duct  into 
the  tooth,  and  thence  into  the  wound. 

The  poison  apparatus  is  constructed  on  the  same 
plan  in  the  common  viper  (Pelias  berus\  not  uncom- 
mon in  Central  and  Southern  Europe,  and  easily  re- 
cognised by  its  dark  green  colour,  and  by  the  zigzag 
black  line  in  the  middle  of  the  back.  Other  poisonous 
snakes  like  the  asp,  the  cobra  di  capello,  and  the  coral 
snake,  have  other  solid  teeth  coexisting  with  the  poi- 
son fangs,  and  some,  like  the  dipsads,  tree  snakes, 'and 
sand  snakes,  have  some  of  the  hinder  teeth  grooved. 
The  poison  of  snake-bites  is  rapidly  fatal,  death 
taking  place  within  an  hour  in  general,  and  it  is  com- 
puted that  over  10,000  deaths  take  place  annually 
from  this  cause  among  human  beings. 

The  water  snakes  inhabit  the  Pacific  and  Indian 
Ocean,  and  have  flat  tails.  They  possess  strong  un- 
grooved  teeth  behind  the  true  poison  fangs.  In  one 
species,  allied  to  the  coral  snake  ( Callophis  inttstinalis), 
the  poison  gland  extends  into  the  abdomen. 

One  curious  group  of  non-poisonous  snakes  pos- 
sess teeth  on  the  anterior  surface  of  the  neck  vertebroe 
in  addition  to  feeble  jaw  teeth.  These  animals  feed 
on  eggs,  and  use  these  teeth  for  breaking  them  while 


Tortoises.  49 

in  the  act  of  swallowing,  so  that  all  the  material  of 
the  egg  may  be  saved  for  food.  Snakes  are  rare  in 
cold  and  more  abundant  in  warm  climates ;  they  are 
also  more  numerous  in  continental  than  in  insular 
regions. 


CHAPTER  X. 

TORTOISES   AND   CROCODILES. 

27.  Order  3,  Chelonia  (Tortoises). — This  order 
consists  of  those  reptiles  whose  bodies  are  enclosed 
in  a  bony  case  composed  of  a  dorsal  or  upper  convex 
shield,  called  the  carapace  and  a  flat  ventral  or  under 
shield,  the  plastron.  The  carapace  is  notched  in 
front  and  behind,  and  between  it  and  the  plastron 
project  the  head  and  neck,  the  limbs,  and  the  tail. 
These  parts  can  be  retracted  under  cover  of  the  bony 
case.  Each  shield  consists  of  a  layer  of  epidermis  or 
tortoise-shell,  and  a  layer  of  bone,  which  in  the  cara- 
pace consists  of  dermal  plates  added  to  the  tops  of 
the  spines  of  the  vertebrae,  the  surfaces  of  the  ribs, 
and  a  row  of  marginal  bony  plates  below  these.  The 
plastron  also  consists  of  nine  plates  of  ossified  dermis 
covered  by  a  symmetrical  series  of  horny  laminae. 
The  skull  is  short,  rounded,  and  not  armed  with 
teeth,  which  are  replaced  by  horny  beak-like  jaws. 
The  lower  jaw  is  in  one  piece  in  the  adult  The 
shoulder-girdle  consists  of  three  bony  rods,  two  in 

£ 


50  Vertebrata. 

front,  and  one  behind  ;  these  are  included  within  the 
carapace,  as  also  is  the  pelvic  girdle. 

FIG.  21. 


Skeleton  ol  European  tortoise,  the  plastron  or  under-shell  removed. 


Crocodiles.  5 1 

The  land  forms  included  under  this  order  are 
tortoises,  such  as  the  common  Greek  tortoise,  which 
live  on  land  and  have  stumpy  feet  with  short  nails. 
The  aquatic  forms  or  turtles,  such  as  the  green  turtle 
used  in  making  turtle  soup,  and  the  hawks-bill  turtle 
used  for  its  '  tortoise  shell,'  are  known  by  their  webbed 
feet  The  largest  tortoises  of  the  present  day  only 
measure  a  few  feet  in  length,  but  in  ancient  days 
tortoises  reached  enormous  sizes ;  thus  the  Colosso- 
chelys,  or  .giant  fossil  tortoise  of  India,  sometimes 
reached  a  length  of  over  thirteen  feet  Tortoises  are 
slow  in  growth,  and  attain  to  extraordinary  ages. 
They  are  for  the  most  part  vegetable  feeders,  differ- 
ing in  this  respect  from  most  other  reptiles. 

28.  Order  4,  Crocodilia.— These,  the  highest  in 
organisation  of  the  entire  class,  are  inhabitants  of  the 
rivers  of  tropical  countries,  and  are  among  the  largest 
of  living  reptiles.  T^ey  have  a  rough,  hard,  scaly 
coat  of  epidermis  which  is  placed  dorsally  on  a 
dermal  bony  surface.  The  vertebral  column  is  pro- 
vided with  ribs,  and  is  composed  of  vertebrae  hollow 
in  front  and  convex  behind.  The  skull  is  long,  and 
covered  with  peculiar  sculptured  markings.  The  teeth 
are  seated  in  sockets  in  one  row,  and  are  renewed 
several  times  in  succession.  The  heart  has  a  com- 
plete septum  or  partition  in  the  ventricle  dividing  it 
into  two  distinct  cavities,  but  the  aortic  arches  still 
communicate  with  each  other  at  their  bases.  The 
feet  are  webbed  and  possess  strong  claws,  and  there 
are  dermal  glands  in  the  throat  secreting  a  peculiar 
musky  material  The  forms  included  are  the  croco- 
diles of  the  Nile  and  Indian  rivers,  with  their  long 

£2 


52  Vertebrata. 

tapering  snouts,  in  which  the  longest  teeth  of  the  lower 
jaw  notch  the  sides  of  the  upper  jaw.  The  alligators 
of  the  New  World  have  heads  oval  or  rounded  in 
front,  and  in  all  of  them  the  lower  jaw  teeth  are 
hidden  by  the  edge  of  the  upper,  when  the  mouth  is 
closed.  The  gavial  of  the  Ganges  has  a  long,  slender- 
pointed  head,  and  is  the  smallest  of  the  group. 

Of  all  the  reptiles  the  crocodiles  are  those  which 
in  point  of  structure  approach  most  closely  to  the 
birds.  They  have  a  gizzard-like  stomach,  a  nictitat- 
ing membrane  in  the  eye,  an  immovable  joint  between 
the  tibia  or  leg  bone  and  the  first  bone  of  the  tarsus 
or  ankle,  a  single  carotid  or  neck-artery,  and  many 
other  structural  peculiarities  which  show  their  super- 
iority over  other  reptiles.  Among  the  orders  of  the 
reptile  class  now  extinct,  there  was  one  which  in- 
cluded bipedal  forms  which  had  possibly  a  kangaroo- 
like  mode  of  progression,  and  one  of  flying  reptiles, 
which  indicated  a  still  closer  relationship  to  the  birds. 


CHAPTER  XI. 

CLASS  IV. — AVES  (BIRDS). 

29.  General  Characters. — These  familiar  verte- 
brates are  characterised  by  possessing  an  epidermal 
clothing  of  feathers,  warm  blood,  a  four-chambered 
heart,  no  teeth,  and  in  general  an  adaptation  for  aerial 
locomotion.  The  mode  of  progression  on  the  earth 


Feathers. 


53 


is  strictly  bipedal,  as  the  fore-limbs  never  touch  the 
ground,  being  modified  into  wings.  Like  reptiles  they 
are  oviparous  and  their  eggs  Fig.  22- 

are  of  large  size  ;  in  most  cases 
also  the  young  are  for  a  certain 
period  under  the  care  of  the 
mother,  by  whose  agency  they 
are  provided  with  food. 

30.  Feathers.  —  Feathers 
are  epidermal  processes  se- 
creted by  long  grooved  papillae 
and  they  are  of  several  sorts. 
The  strong  distinct  feathers, 
which  have  a  central  axis  and 
lateral  expansions  or  vanes,  are 
called  contour-feathers,  while 
the  smaller  soft  feathers  which 
clothe  the  intimate  surface  of 
the  skin,  which  have  soft  or 
woolly  processes  and  no  axis, 
are  called  down-feathers.  In 
each  contour-feather  we  notice, 
firstly,  the  hole  at  the  base  (fig. 
22,  e)  where  it  is  thickened 
around  the  base  of  the  papilla ; 
secondly,  the  slit-like  hole,  f, 
marking  the  region  above  which 
the  sheath  of  the  papilla  has 
split ;  thirdly,  the  rachis,  or  the 
square  solid  axis,  b  ;  fourthly, 

the    flat    expanded*  lamina,    Or    «,  barrel;  b,  rachis;  c,  vanes; 

vane,  c,  composed  of  separate 
barbs,  the  margins  of  each  of 


Contour-feather. 


54  Vertebrata. 

which  are  joined  to  their  neighbours  by  numerous 
booklets. 

In  this  respect  contour-feathers  differ  from  down, 
in  which  the  barbs  are  all  discontinuous.  In  young 
birds  the  entire  plumage  consists  of  simple  down- 
feathers  covering  the  whole  surface  almost  uniformly, 
and  in  some  birds  which  do  not  possess  the  power  of 
flight,  this  condition  is  more  or  less  perpetuated,  and 
thus  all  the  feathers  have  discontinuous  barbs,  as  in 
the  ostriches.  In  the  great  majority  of  birds,  how- 
ever, this  primitive  surface  clothing  is  shed  and  be- 
comes replaced  by  a  second  growth  of  feathers,  which 
differs  from  the  first  in  that  the  component  feathers 
are  for  the  most  part  contour-feathers,  arranged  in 
definite  tracts,  and  between  these  pterylce,  or  feather 
tracts,  there  are  spaces  quite  devoid  of  contour-feathers. 
In  the  course  of  life,  many  birds  change  their  feathers 
several  times,  the  process  being  called  '  moulting.' 
To  defend  the  feathers  from  the  influence  of  moisture 
there  is  a  gland  situated  on  each  side  of  the  tail  bone 
which  secretes  an  oily  material  of  use  in  lubricating 
the  plumage.  The  largest  feathers  are  those  of  the 
wing,  and  they  are  grouped  into  primaries,  secondaries, 
and  tertiaries,  according  as  they  are  borne  respectively 
by  the  hand,  the  lower,  or  the  upper  end  of  the  fore- 
arm ;  over  these  are  the  scapulars,  and  on  the  rudi- 
mental  thumb  is  the  alula.  The  tail  feathers  are 
also  long,  and  as  they  are  used  in  steering  they  are 
named  rectrices  to  distinguish  them  from  the  oar- 
feathers  of  the  wing. 

The  papillae  which  secrete  the  feathers  are  long, 
vascular,  and  deeply  grooved  on  the  surface ;  the 


Plumage  and  Skeleton  of  Birds.  5  5 

protoplasmic  matter  exuded  by  the  surface  of  the 
papillae  is  collected  into  these  channels,  it  then  hardens 
and  forms  in  the  first  place  a  hollow  cylinder  of  horny 
matter,  with  ridges  fitting  into  the  papillary  grooves 
and  thin  areas  between.  As  growth  takes  place  most 
actively  at  the  base  of  the  papilla,  this  horny  sheath 
is  pushed  off  the  surface  of  the  papilla,  upon  which  it 
shrinks  still  more,  and  the  horny  cylinder  splits  along 
its  thinnest  side,  whereupon  the  two  lateral  laminae 
flatten  out  as  the  vanes,  while  the  rib  which  corre- 
sponded to  the  main  groove  of  the  papilla  becomes 
the  rachis.  The  feathers  of  many  birds  are  of  brilliant 
colours,  usually  brighter  in  the  males  than  in  the 
females. 

31.  Bones. — The  skeleton  of  birds  is  well  adapted 
for  their  aerial  existence.  The  skull  is  early  consoli- 
dated, and  articulates  with  the  spine  by  one  occipital 
condyle.  The  ten  or  twelve  parts  of  the  lower  jaw 
are  also  early  united  into  a  single  piece  and  the  front 
of  the  jaw  is  enclosed  in  a  horny  sheath ;  it  articulates 
to  the  skull  by  means  of  a  movable  quadrate  bone 
which  is  kept  in  its  place  by  two  rods  of  bone,  one 
on  the  outside  stretching  from  the  base  of  the  upper 
beak  (the  jugal  arch),  the  other  on  the  inside  stretch- 
ing from  the  palate  (the  pterygoid  arch).  The  upper 
mandible,  or  beak,  is  also  encased  in  a  horny  layer 
at  whose  base  are  the  nostrils,  very  often  surrounded 
by  a  thick  leathery  skin,  which  is  called  the  cere. 

The  neck  is  usually  long  and  exceedingly  flexible, 
made  up  of  from  nine  to  twenty- three  vertebrae  ;  its 
length  and  that  of  the  bill  usually  bears  some  propor- 
tion to  the  length  of  the  legs.  The  breast-bone  bears 


56  Vertebrata. 

in  front  a  prominent  keel,  to  which  the  muscles  which 
elevate  and  depress  the  wing  are  attached,  and  this  is 
only  absent  in  such  birds  as  do  not  fly,  as  the  ostrich, 
emu,  and  New  Zealand  ground  parrot.  The  wings 
are  fastened  to  a  very  strong  shoulder-girdle,  which 
consists  of  three  parts  ;  firstly,  of  a  V-shaped  furculum, 
or  merrythought,  which  consists  of  the  two  collar- 
bones united  together  in  the  middle  line  ;  secondly, 
FIG.  23.  of  the  coracoid  bone,  a  stout 

bony  rod  which  fits  into  a 
groove  in  the  top  of  the 
breast-bone  and  stretches 
from  thence  upwards  and 
backwards  to  the  shoulder 
joint ;  thirdly,  the  scapula,  or 
scythe-blade-like  bone,  which 
j  joints  with  the  coracoid  at 
the  shoulder,  and  descends 
backwards  over  the  dorsal 
ribs,  slung  in  its  place  by 
muscles.  The  wing  bones 
consist  of,  firstly,  an  arm 
bone,  or  humerus ;  secondly, 
Pelvis  of  bird.  two  forearm  bones  ;  thirdly, 

a,  sacrum ;    b,   lumbar  vertebras ;  i  •  i         j     i          i 

d,  ilium ;  /,  pubis ;  g,  sciatic  a  consolidated   hand   made 
up  of  several  (never   more 

than  four)  united  fingers,  of  which  only  the  thumb  in 
general  bears  a  claw,  rarely  the  thumb  and  index 
fingers,  as  in  the  cassowary.  The  ribs  are  few  and 
are  fastened  together  by  lateral  spurs,  or  processes. 
The  portions  of  the  ribs  which  articulate  with  the 
vertebral  column  are  separate  from  those  that  unite 
with  the  breast  bone. 


Feet  of  Birds.  5  7 

The  tail  bones  are  short  and  compressed,  forming 
a  ploughshare-like  process  ;  the  pelvic  bones  are  long, 
and  stretch  along  the  spine  fore  and  aft  to  an  extent 
proportionally  unmatched  in  the  rest  of  the  sub-king- 
dom (fig.  23).  The  two  pubic  bones  do  not  unite  in 
the  middle  line  in  front  of  the  pelvis  except  in  the 
ostrich,  but  always  remain  separate  and  open.  The 
thigh  bones  are  short.  The  leg-bone  consists  of  two 
parts,  which  in  adult  birds  are  indistinguishably  united. 
Of  these  the  largest  part  is  the  tibia,  or  leg-bone 
proper,  the  lower  end  consists  of  the  astragalus,  or 
first  bone  of  the  tarsus  or  ankle.  The  lower  part  of 
the  shank  of  a  bird  consists  of  the  remaining  tarsal 
and  metatarsal  bones  elongated  into  a  single  shaft, 
and  below  this  are  the  toes,  of  whiqh  usually  four  are 
developed.  The  innermost  of  these  or  the  hind  .toe 
consists  in  general  of  two  joints  or  phalanges,  the 
second  (inner)  toe  is  made  up  of  three,  the  middle 
or  longest  toe,  of  four,  and  the  outermost  toe  of  five 
phalanges.  The  shapes  and  dispositions  of  the  toes 
vary  with  the  habits  of  the  birds  ;  thus,  birds  of  prey 
have  stout,  grasping  feet,  with  sharply  hooked  claws. 
Climbers,  like  woodpeckers  and  parrots,  have  the 
outer  and  inner  toes  turned  backwards  and  the  other 
two  forwards.  In  swimmers,  all  the  forward  toes  are 
webbed,  while  in  the  scraping  birds  the  toes  are 
short,  stout,  and  armed  with  blunt  nails.  Many  of 
the  bones  in  the  body  of  a  bird  are  hollow,  and  in- 
stead of  containing  marrow  they  are  lined  by  a  deli- 
cate membrane  and  contain  air,  which  is  conducted 
into  them  from  the  respiratory  organs  by  thin  walled 
canals.  This  condition  is  specially  exhibited  in  the 


58  Vertebrata. 

birds  of  most  powerful  flight,  but  the  bones  of  very 
young  birds  contain  marrow. 

32.  Muscles  and  Viscera. — The  muscle  or  flesh 
of  birds  consists  of  very  close  fibres,  and  the  sinews 
or  tendons  are  often  converted  into  bone.  There  is 
an  enormous  muscle  on  the  front  of  the  breast,  the 
great  pectoral,  whose  action  is  to  depress  the  wing ; 
beneath  this  is  a  smaller,  or  second  pectoral  muscle 
with  oblique  fibres,  arranged  like  the  barbs  of  a  feather, 
and  converging  to  a  tendon  which,  winding  round  a 
pulley  at  the  top  of  the  coracoid,  is  inserted  into  the 
top  of  the  humerus  and  raises  the  wing ;  this  is  the 
second  pectoral.  In  the  legs  of  many  birds  there  is 
to  be  found  superficially  on  the  front  of  the  thigh  a 
slender  little  muscle,  which,  starting  from  the  front  of 
the  pelvis,  passes  down  the  upper  or  front  surface  of 
the  thigh,  winds  round  to  the  back  of  the  knee  and 
runs  by  a  tendon  into  the  superficial  flexor  (or  bender) 
muscle,  for  the  longest  toe  (plantaris) ;  a  second 
muscle  (the  peroneus),  from  the  outside  of  the  leg  can 
generally  be  traced  into  the  same  toe-muscle.  These 
muscles  are  supposed  to  be  of  importance  in  the 
action  of  perching,  and  as  their  tendons  pass  over 
several  joints  they  probably  have  a  complex  action. 

The  digestive  system  of  birds  consists  of  the  fol- 
lowing parts  :  first,  the  bill  or  prehensile  organ,  vary- 
ing in  shape  and  texture  according  to  the  nature  of, 
and  mode  of  obtaining,  the  food  upon  which  the  bird 
subsists ;  secondly,  the  tongue,  rarely  soft,  usually 
hard  and  horny,  often  barbed  ;  thirdly,  the  long  food- 
passage,  or  oesophagus,  which,  above  the  furculum, 
usually  dilates  into  a  crop  (fig.  24,  #),  below  which  is 


Viscera  of  Birds. 


59 


a  glandular  stomach  (c)  communicating  with  the 
gizzard,  or  true  muscular  stomach  (c).  This  cavity 
has  a  thick  muscular  wall  consisting  chiefly  of  two 
masses  of  muscle  united  by  a  strong  tendon,  and 
lined  by  a  rough  horny  cuticle  ;  into  this  birds  fre- 
quently introduce  small  stones  which  assist  in  tri- 
turating or  grinding  the  food,  as  this  organ  is  chiefly 
the  place  where  the  material  of  the  food  is  reduced 

FIG.  24. 


b,  crop  :  i;  c,  glandular  stomach  and  gizzard. 

mechanically  to  a  condition  of  pulp  to  prepare  it  for 
further  digestive  changes.  The  gastric  juice  secreted  in 
the  glandular  stomach  is  here  thoroughly  mixed  up 
with  it,  and  the  food  mass  is  thus  prepared  for  the 
intestinal  canal.  The  gizzard  is  especially  strong  in 
grain,  or  fruit-eaters,  weak  or  absent  in  flesh-eaters. 

Birds  have  two  separate  ventricles  in  the  strong 
muscular  heart ;  one  on  the  right  side  for  propelling 


6o 


Verlebrata. 


the  impure  or  venous  blood  of  the  right  auricle  into 
the  lungs,  and  the  other,  or  left  ventricle,  for  driving 
the  purified  blood  after  its  return  from  the  lungs, 
through  the  body ;  the  opening  into  the  right  ventri- 
cular cavity  from  the  auricle  is  guarded  by  a  muscular 
flap.  There  is  only  one  aortic  arch  developed  in  the 
adult  bird,  and  it  arches  to  the  right  side,  and  in  many 
birds  there  is  only  one  artery  developed  in  the  neck 
for  the  supply  of  the  head.  The  lungs  are  large,  and 
surrounded  on  their  lower  surfaces  by  large  air-sacs, 
into  which  the  bronchial  tubes  distinctly  open ;  from 
these  cavities  pass  the  membranous  canals,  which 
convey  the  air  to  the  principal  bones.  There  is  no 
muscular  layer  underlying  the '  lungs  for  the  purpose 

FIG.  25. 


Organ  of  voice  of  the  raven. 
A,  front  view  ;  B,  side  view  showing  the  muscles  of  vocalisation. 

of  directly  acting  on  them  in  respiration,  except  in  the 
ostrich  and  apteryx  ;  but  as  the  sternal  and  vertebral 


Voice  and  Senses  of  Birds.  6 1 

ribs  can  move  on  each  other,  the  bony  wall  of  the 
thorax  or  chest  cavity  is  susceptible  of  a  large  range  of 
motion  for  breathing. 

As,  from  the  activity  of  their  motion,  birds  require 
a  more  perfect  system  of  nutrition  for  their  ultimate 
tissues  and  organs  than  reptiles,  their  respiratory 
apparatus  is  very  highly  developed,  and  hence  their 
temperature  is  higher  than  that  of  any  other  group  of 
animals. 

An  organ  of  voice  is  usually  developed  in  the 
air-passages  of  birds,  most  commonly  at  the  point 
where  the  windpipe  or  trachea  bifurcates  to  send  an 
air-tube  to  each  lung  (fig.  25).  At  this  spot  there  is 
a  drum-like  cavity  or  syrinx  (g),  in  which  certain  tense 
membranes  can  be  made  to  vibrate,  and  can  be  acted 
on  by  muscles  (a,  b,  c,  */,  e\  attached  to  the  windpipe. 
Thus  the  organ  differs  from  that  in  mammals,  in 
which  the  seat  of  voice  is  the  larynx  or  upper  end 
of  the  windpipe.  In  the  wild  swan  the  long  and 
sinuous  windpipe  is  contained  in  a  hollow  which  is 
provided  for  its  reception  in  the  keel  of  the  sternum. 

The  blood  of  birds  contains  small  elliptical  cor- 
puscles which  are  nucleated. 

The  eye  of  birds  is  remarkable  for  possessing 
bony  plates  in  its  '  white/  as  well  as  a  curious  folded 
vascular  projection  at  the  bottom  of  the  eyeball,  which 
projects  forwards  towards  the  crystalline  lens.  There 
is  also  a  third  eyelid,  or  nictitating  membran",  placed 
below  and  within  the  two  ordinary  lids,  and  moved  by 
two  little  muscles  on  the  back  of  the  eyeball,  and 
there  is  an  additional  gland  whose  secretion  keeps 
this  accessory  lid  moist  The  senses  of  smell  and 


62  Vertebrata. 

hearing  are  also  largely  developed  in  some  birds, 
notably  in  vultures  and  owls,  the  latter  being  pro- 
vided with  a  distinct  external  ear. 

Most  birds  have  but  one  oviduct,  and  that  is  on 
the  left  side ;  in  its  lining  there  are  glands  which 
secrete  the  white  of  the  egg,  its  membrane,  and  the 
shell,  during  the  downward  passage  of  the  yolk.  The 
embryonic  bird  is  provided  with  a  rudimental  knob 
on  its  pre-maxillary  bones,  which  it  uses  in  breaking 
the  egg-shell  wherein  it  is  contained. 


CHAPTER  XII. 

CLASSIFICATION   OF   BIRDS. 

33.  Primary  Divisions. — About  8,000  species  or 
birds  are  known  to  the  naturalist,  and  these  are  divided 
into  two  primary  sub-classes. 

The  first  sub-class  is  called  Ratidce,  and  includes 
all  those  birds  which  have  a  sternum  without  a  keel,  a 
rudimentary  furculum  and  wings,  feathers  with  discon- 
tinuous barbs  and  not  distributed  in  feather  tracts, 
and  with  no  oil  gland.  They  are  all  natives  of  warm 
or  temperate  climates,  and  strictly  limited  in  their 
range.  Several  gigantic  forms  which  existed  until 
recently,  are  now  extinct,  such  as  the  moa  of  New 
Zealand  and  the  sepyornis  of  Madagascar.  The 
ostrich  of  Africa  is  a  familiar  instance,  and  is  pro- 
vided only  with  two  toes.  The  American  ostrich 
or  rhea  is  smaller,  and  inhabits  South  America. 


Parrots  and  Cuckoos.  63 

The  cassowary  is  a  native  of  the  East  Indian  archi- 
pelago, and  the  emu  of  the  Australian  continent. 
The  apteryx  of  New  Zealand  is  the  most  remarkable 
of  these  birds,  as  it  has  perfectly  rudimentary  wings 
and  a  long  slender  bill,  and  there  is  a  remarkable 
disproportion  between  the  size  of  the  egg,  which  is 
very  large,  and  that  of  the  bird. 

The  second  sub-class  of  birds  is  called  Carinata 
and  includes  all  those  birds  which  have  a  keel  on  the 
breast -bone,  a  merrythought,  usually  functional 
wings,  whose  feathers  are  in  tracts  (except  in  the 
penguins)  and  have  the  barbs  united  along  their 
margins.  This  includes  fourteen  orders  of  birds,  of 
many  of  wrhich  there  are  familiar  illustrations  easily 
obtainable. 

34.  Order  1,  Parrots  (Psittaci). — The  most  in- 
telligent and  most  highly  organised  of  birds ;  easily 
known  by  their  sharply  FIG.  26. 

hooked  beaks,  both  the 
upper  and  lower  part  of 
which  are  movable,  and 
by  their  brightly-coloured 
feathers.  Their  feet  are 
prehensile,  the  outer  and 
inner  toes  being  turned  ~^kull  of  ~ 

backwards,  while    the  tWO    Mj  nostril ;  e,  quadrate  bone ;  v.  lower 

middle    toes   are    turned 

forwards,  and  thus  they  are  enabled  to  grasp  in  climb- 
ing. The  tongue  is  soft,  and  the  muscles  which  move 
it  are  more  distinct  thai*  those  of  most  birds,  and 
hence  the  singular  power  of  mimicking  sounds  pos- 
sessed by  many  of  them.  They  are  natives  of  the 


64  Vertebrata. 

•\ 

tropics,  the  cockatoos  being  mostly  from  the  East 
Indian  archipelago,  the  macaws  from  South  America, 
the  common  parrots  from  Africa  and  Madagascar. 
One  curious  genus,  Strigops,  the  ground  parrot  of 
New  Zealand,  is  exceptional  in  having  no  keel  on  its 
sternum,  and  some  parakeets  from  Australia  have  no 
merrythought.  They  are  vegetable-feeders,  princi- 
pally subsisting  on  fruits,  but  often  eating  honey. 
Many  species  live  long  in  confinement,  and  they  are 
all  easily  domesticated. 

35.  Order  2,  Cuckoos,  &c.  (Coccygomorphae). — 
These  are  usually  long-beaked  birds  with  small  flat 
tongues,  having  the  toes  arranged  either  permanently 
or  temporarily  like  those  of  parrots,  with  the  outer 
and  inner  turned  backwards.     The  wings  have  long 
covering  feathers.     Some  of  these  birds  have  enor- 
mous beaks  thrice  as  long  as  the  head,  like  the  little 
toucans  of  America ;   in  others   the  beaks  are  sur- 
mounted  with   great  horns,   made  of  spongy  bony 
tissue  covered  with  horn,  as  in  the  hornbills  of  the 
Eastern  tropics.     Other  examples  of  this  order  are 
the  cuckoos,  so  familiar  for  their  peculiar  note  and  for 
their  habit  of  laying  eggs  in  the  nests  of  other  birds  ; 
the  kingfishers,  bee-eaters,  hoopoe,  rollers,  &c.    Some 
are   remarkable   for  their  colours,  like  the  plantain - 
eaters  of  Africa.    The  tongues  are  hard,  often  bristled, 
as  in  the  toucans;  few  have  much  vocal  power.     They 
are  for  the  most  part  feeders  on  insects  and  animal 
substances. 

36.  Order    3,    Woodpeckers    (Pici),  —  Mostly 
brightly-coloured  birds,  with  straight,  strong,  conical 
beaks,  and  slender  and  actively  protrusible  tongues. 


Swifts  and  Humming  Birds.  65 

The  wings  have  short  coverts.  The  middle  toes  are 
united  at  the  base ;  the  inner  toe  is  small,  directed 
backwards,  as  is  also  the  outer  r,G.  27. 

toe.  The  tail  feathers  are  short, 
stiff,  and  serve  as  organs  of 
support.  These  are  insect-eat- 
ing birds  like  the  last  group, 
and  they  derive  their  name  from 
their  efforts  after  the  capture 
of  their  prey,  fn  these  the 
tongue  bone  is  specially  elon- 
gated, and  its  lateral  processes 
coiled  and  disposed  to  allow 
of  the  rapid  protrusion  of  the 

,IT       j         i  Foot  of  woodpecker. 

barbed  tongue.     Woodpeckers 

exist  everywhere  but  in  Madagascar  and  Australia. 

37.  Order  4,  Swifts  and  Humming-Birds  (Macro- 
chires). — A  small  order  of  birds,  mostly  of  very 
minute  size,  and  almost  all  of  powerful  flight.  Some 
of  these,  like  the  swifts,  have  flattish  beaks;  others, 
like  the  humming-birds,  have  long  tubular  bills.  In 
each  wing  the  forearm  and  hand  greatly  exceed  in 
length  the  upper  arm,  hence  the  I,atin  name  given  to 
the  order.  The  feet  are  very  weak,  scarcely  able  to 
support  the  weight  of  the  body,  and  the  inner  toe 
may  in  some  be  turned  forwards  or  backwards.  They 
have  a  very  simple  syrinx,  and  little  or  no  voice. 
They  are  mostly  tropical  birds,  and  vary  much  in 
size,  the  goatsuckers  being  the  largest,  sometimes  of 
comparatively  large  size  ;  while  the  swifts  are  much 
smaller  and  somewhat  swallow-like.  One  of  these, 
the  Collocalia  of  the  Malay  archipelago,  secretes,  by 


66  Vertebrata. 

means  of  glands  in  the  throat,  a  glutinous  material  of 
which  it  constructs  its  nests,  which  are  the  edible 
birds'  nests  of  Eastern  commerce,  used  as  food  in 
China.  The  humming-birds  of  Brazil,  of  which  there 
are  very  numerous  species,  are  also  examples  of  this 
order,  and  include  the  smallest  forms  of  the  entire 
class  of  birds;  thus  Mclisuga  minimus,  from  the  island 
of  San  Domingo,  only  weighs  about  nine  grains,  and 
measures  two  inches  in  extreme  length ;  its  nest  is 
about  the  size  of  a  walnut,  and  it  contains  two  eggs 
each  nearly  as  large  as  a  pea. 

38.  Order  5,  PercMng  birds  (?asseres.)— This 
large  order  includes  all  our  small  birds,  with  the  ex- 
ception of  those  hitherto  mentioned.     They  may  be 
recognised  by  possessing  short  wing  coverts,  a  tarsus 
FIG.  28.  covered  in  front  with  seven  large 

scales,  and  slender  toes,  of  which 
the  first  joints  of  the  two  outer  are 
united.  They  have  a  well-deve- 
loped syrinx  or  organ  of  voice,  and 
many  of  them  can  sing.  These  birds 
are  very  numerous,  and  make  up 

Foot  of  passerine  bird.        ,  .....  . 

about  twenty-one  families.  The 
best  known  of  these  are  the  following  : — The  thrushes, 
known  by  their  slightly  curved  bill,  with  a  notch  or 
tooth  on  each  side  near  the  tip,  and  with  bristles  at 
the  angles  of  the  gape  of  the  mouth.  They  are 
insect-eaters  for  the  most  part.  The  commonest 
species  are  the  song  thrush;  the  blackbird,  known 
by  its  yellow  bill  and  eyelid-edge  and  its  black 
body ;  the  missel  thrush,  known  by  its  white-tipped 
three  outer  tail  feathers  ;  the  fieldfare,  the  redwing. 


Passerine  Birds.  67 

To  this  family  belongs  the  mocking  bird  of  America, 
which  can  mimic  the  song  of  any  other  bird.  The 
birds  of  the  wagtail  family  are  recognisable  by  their 
slender  forms,  long  legs,  long  tails,  and  moderate 
wings  with  nine  primary  feathers.  They  include  the 
common  pied  wagtails,  the  yellow-breasted  wagtail ; 
closely  allied  to  which  are  the  hedge-sparrows  (Ac- 
centor) with  strong,  sub-conical,  straight  bills,  and 
wings  with  a  very  short  first  quill,  the  third  and  fourth 
primaries  being  the  longest.  The  warbler  family, 
consisting  of  small  singing  birds  with  awl- shaped 
beaks  flattened  at  base,  are  also  closely  allied ;  of 
these  the  most  familiar  examples  are  the  nightingales 
(Philomela] ;  robin  red-breasts  of  Europe ;  red-starts 
(Phanicura)  ;  sedge  and  grasshopper  warblers  (Sal- 
icaria)  ;  white-throats,  black-caps  (Curruca) ;  and 
willow-wrens  (Sylvia).  The  gold-crested  kinglet 
(Regulus)  is  the  smallest  American  bird  of  this  order, 
its  length  being  under  4  inches.  The  pipits  (Anthus), 
have  awl-shaped  bills,  keeled  at  the  base  above,  with 
two  long  scapular  feathers  and  long  hind  claw.  In 
North  America  the  warblers  (Silviidce)  of  Europe  are 
represented  by  the  Sihricolida  or  American  warblers. 
The  crow  family  (Corvida)  constitute  a  group  of 
much  larger  birds  ;  they  have  strong  conical  bills  with 
no  notch,  and  robust  feet.  This  family  includes  the 
jackdaw,  crow,  raven,  jay,  and  magpie,  and  the  star- 
ling is  a  nearly  related  form.  These  have  ten  pri- 
mary feathers,  while  the  birds  of  the  conical-billed 
finch  family  possess  only  nine.  This  family  consists 
of  the  house-sparrows,  hawfinches,  linnets,  bullfinches, 
and  nearly  related  are  the  larks  and  buntings. 

F  2 


68  Vertebrate. 

Among  the  most  remarkable  tropical  forms  are 
the  lyre-birds  of  Australia,  the  oven-builders  of  Brazil ; 
the  sun-birds,  nuthatch,  wax-wings,  &c. 

39.  Order  6,  Birds  of  Prey  (Raptores). — This 
order  consists  of  eagles,  owls  and  vultures,  which 
feed  on  animal  food,  and  are  armed  with  strongly 
hooked  bills  (fig.  30),  and  with  strong,  sharp  and 
curved  claws  (fig.  29).  At  the  base  of  the  bill  is  a 

Fig.  29.  FIG.  30 


Foot  of  eagle.  Head  of  eagle. 

cere  or  skin,  which  is  pierced  by  the  nostrils.  The 
gizzard  is  weak,  the  digestive  tract  short,  the  sense 
organs  are  acute  and  powerful.  Their  strong  wings 
have  ten  primary  feathers,  and  the  tail  has  twelve 
rectrices.  Owls  are  mostly  nocturnal,  round-faced 
birds,  with  short  beaks,  and  with  eyes  directed  for- 
wards. They  have  no  crop,  and  peculiarly  soft  plu- 
mage. Some  have  tufts  of  feathers  above  the  ears, 
such  as  the  horned  owls.  Vultures  are  carrion-eaters, 
most  abundant  in  warm  climates,  with  naked  or  down- 
clad  head  and  longer  bills.  Eagles  have  feather- 
clad  heads,  and  short,  sharply-hooked  bills,  and  they 
for  the  most  part  feed  on  prey  which  they  kill  for 


Pigeons  and  Poultry.  69 

themselves.  To  this  family  belong  the  hawks,  kites, 
buzzards  and  harriers,  as  well  as  the  larger  eagles, 
ospreys,  and  falcons. 


CHAPTER  XIII. 

CLASSIFICATION   OF   BIRDS    CONTINUED. 

40.  Order  7,  Pigeons  (Gyrantes). — This  well- 
marked  group  consists  of  the  doves  and  pigeons, 
characterised  by  having  a  gristly  plate  covering  the 
base  of  the  upper  mandible,  pierced  in  front  by  the 
nostrils.  They  are  vegetable-feeders,  with  a  large 
glandular  crop  which  sometimes  secretes  a  milky  fluid 
with  which  the  parents  nourish  the  young  birds. 
They  have  a  strong  gizzard,  shielded  or  feathered 
tarsi,  and  four  usually  free  toes  all  on  the  same  level, 
with  short,  slightly-hooked  claws.  They  are  mostly 
birds  of  powerful  flight,  and  have  ten  primary  quill 
feathers  in  their  long  pointed  wings,  and  twelve  or 
rarely  sixteen  rectrices.  They  are  mostly  social  birds, 
often  living  in  great  societies.  The  pigeons,  wood- 
quests,  and  doves  are  familiar  instances,  as  also  are 
the  passenger  pigeons  of  North  America,  which  mi- 
grate in  millions,  darkening  the  air  by  their  flocks. 
Our  common  pigeons,  in  all  their  varieties,  are  de- 
scended from  the  rock-dove,  Columba  livia.  The 
curious  dodo  of  Mauritius  was  an  aberrant  large 
pigeon  incapable  of  flight,  and  hence  it  was  easily 


70  Vertebrata. 

captured  by  the  early  voyagers,   and  was  extirpated 
in  the  seventeenth  century. 

41.  Order  8,   Scraping   birds    (Rasores). — This 
large  and  economically  important  order  includes  the 

FIG.  31.  poultry,      turkeys,      pheasants, 

grouse,  partridge,  &c.,  heavy 
plump-bodied  birds,  with  com- 
paratively small  rounded  wings, 
weak  in  flight,  and  with  a  mode- 
rate length  of  beak  and  legs; 
they  have  stout  blunt  claws,  the 
hind  toe  being  raised  above  the 
level  of  the  others.  The  name  of  the  order  is  derived 
from  the  habit  common  to  most  of  them  of  scraping 
in  searching  for  their  food  in  or  on  the  ground.  The 
tarsus  often  bears  spurs,  especially  in  the  males,  and 
the  plumage  is  close  and  often  brilliantly  coloured,  as 
in  the  peacocks  and  pheasants.  Many  of  them  have 
naked  areas  on  the  head,  where  the  skin  is  soft 
and  vascular,  forming  wattles  or  crests.  As  they  are 
mostly  grain-eaters,  they  have  large  muscular  gizzards, 
capacious  crops,  and  long  intestines.  Our  common 
domestic  fowls  are  natives  of  India,  as  also  is  the 
peacock  and  that  most  gorgeously  coloured  bird  the 
Impeyan  pheasant,  whose  plumage  has  a  rich  metallic 
lustre.  The  golden  pheasant  is  a  native  of  China,  the 
turkey  of  America.  In  Australia  the  order  is  repre- 
sented by  the  mound-birds  and  brush  turkeys,  which 
hatch  their  eggs  in  '  hot-beds '  formed  of  large  masses 
of  decaying  vegetable  matters  which  they  heap  together 
for  the  purpose. 

42.  Order  9,  Grallae. — This  group  consists  of  long- 


Storks  and  Ducks.  7 1 

legged  birds  which  are  often  waders  in  habit,  and 
are  characterised  by  possessing  small  hind  toes  and 
long  bills.  They  feed  on  worms,  molluscs,  and  fish, 
rarely  on  vegetables.  The  side  of  the  head  presents 
no  bare  patch  between  the  angle  of  the  mouth  and 
the  eye,  and  the  palate  exhibits  a  long  cleft  between 
the  two  lateral  halves  of  the  upper  jawbones.  To  this 
order  belong  the  plovers  and  peewits,  coots  and 
waterhens,  corncrakes  and  snipe,  the  cranes  and 
bustards,  oyster-catchers,  herons,  and  bitterns. 

43.  Order  10,  Storks  (Ciconise).— This  group  also 
consists  of  birds  with  long  legs  and  bills,  which  in 
habit  resemble  the  last,  but  differ  from  them  essen- 
tially in  their  structure.  Thus  they  have  the  two 

FIG.  32.  B 


Head  of  ibis.  Foot  of  ibis. 

lateral  sides  of  the  upper-jaw  united  along  the  middle 
line  of  the  palate  ;  the  lore  or  space  between  the 
angle  of  the  mouth  and  the  eye  is  bare,  and  the  hind 
toe  is  long  and  functional.  The  best  known  examples 


72  Vertebrata. 

are  the  ibises,  spoonbills,  storks,  and  jabirus,  some  of 
which  are  distinguished  for  their  brilliant  colours, 
like  the  scarlet  ibis,  the  straw-necked  ibis,  and  the 
scarlet  spoonbill.  The  loose  feathers  of  the  lepto- 
ptilus  of  India  are  used  for  ornamenting  bonnets, 
under  the  name  Marabou  feathers. 

44.  Order  11,  Ducks  and  Geese  (Lamellirostres). 
— The  birds  belonging   to   this  order   make  a  very 
natural  assemblage  characterised  by  possessing  webbed 
feet  and  long  flattened  bills,   which   on  the   under 
surface  of  the  upper  mandible  exhibit  a  series  of  close 
transverse  lamellae ;  these  act  as  sensitive  prehensile 
surfaces  in  feeding,  and  large  nerves  are  distributed 
on  them.     They  have  large  fleshy  tongues,  and  the 
hind  toe  is  free  and  small.     The  wild  swan  presents 
a  curious  arrangement  of  its  very  long  and  sinuous 
windpipe,  a  coil  of  which  lies  within  the  hollow  keel 
of  the  sternum.    The  best  known  forms  are  the  ducks, 
geese,  mergansers,  swans,  teals,  widgeon,  £c. 

45.  Order  12,  Longipennes.—  These  are  also  web- 
footed   marine   fish-eating  birds,  with  long  pointed 
wings  well  fitted  for  flight     They  have   long  com- 
pressed beaks,  with  the  nostrils  either  slit-like,  as  in 
the  common  gull,  or  tubular,  as  in  the  petrel.     The 
hind  toe  is  free,  and  usually  of  small  size. 

The  gulls,  terns,  petrels  are  the  best  known 
examples,  the  largest  species  in  the  order  being  the 
famous  albatross,  found  on  the  ocean  about  the 
equator,  which  is  allied  to  the  small  petrels  or  Mother 
Gary's  chickens. 

46.  Order    13,     Pelicans     (Steganopodes). — A 
curious  order  of  water  birds  which  have  all  the  four 


Penguins. 


73 


toes  included  in  the  broad  web,  hence  the  feet  have 
a  singularly  inturned  appearance  (fig.  33).  Many  of 
them  have  long  bills  and  throat  FIG.  33. 

pouches,  like  the  pelicans  and  fri- 
gate birds ;  other  and  better  known 
forms  are  the  gannets,  cormorants, 
and  long-tailed  tropic  birds. 

47.  Order    14,    Pygopodes. — 
The  last  order  of  birds  includes  a 
singular  assemblage    of   seabirds, 
whose  wings  are  small  and  sickle- 
shaped,  scarcely  fitted   for   flight, 
and  sometimes  with  scale-like  fea- 
thers, as  the  penguins  of  the  Ant- 
arctic Ocean.    They  have  the  hind 
limbs  even  farther  back  than   in 

the  generality  of  seabirds,  and  hence  the  curious  erect 
position  assumed  by  these  birds  when  standing ;  they 
have  hard  pointed  compressed  bills,  and  a  small  hind 
toe,  the  three  anterior  toes  are  closely  webbed.  The 
auks  of  the  northern  seas,  the  puffins,  guillemots,  and 
razorbills  of  our  shores,  are  the  most  familiar  examples. 
The  great  auk  of  the  northern  seas,  is  wingless,  and 
like  the  dodo  has  become  extinct. 

48.  Migration  of  Birds. — Among  birds,  as  among 
fishes,  we  notice  the  curious  habit  of  periodical  mi- 
gration ;  the  travelling  at  regular  periods  into  districts 
wherein  suitable  food  is  abundant,  and  their  return 
on  change  of  season ;  thus  the  swallows,  swifts,  rice 
birds   and  warblers  visit  the  north  about  the   middle 
of  April,  breed  there,  and  then  return  to  their  winter 
quarters  in  the  Southern  States  and  the  West  Indies 


74  Vertebrata. 

on  the  advent  of  cold  weather,  about  the  first  week  of 
October. 


CHAPTER  XIV. 

CLASS   5,    MAMMALIA. 

49.  General  Characters. — This,  the  highest  class 
of  vertebrate  animals,  includes  all  those  viviparous, 
warm-blooded  animals  which  are  provided  with  super- 
ficial dermal  glands  for  the  purpose  of  secreting  a 
fluid  called  milk  for  the  nutrition  of  the  young  until 
they  are  able  to  seek  out  other  nutriment  for  them- 
selves. They  are  for  the  most  part  terrestrial  in  habit ; 
they  are  all  provided  with  epidermal  covering  in  the 
form  of  hairs  ;  and  the  lower  jaw  in  them  articulates 
directly  with  the  base  of  the  skull,  the  quadrate  bone 
being  very  small  and  included  in  the  ear  cavity,  so 
that  it  is  of  use  only  in  conveying  sound-waves  to  the 
nerves  of  hearing.  Man,  all  quadrupeds,  seals,  whales, 
and  bats  are  examples  of  this  class. 

The  superficial  clothing  of  hairs  characteristic  of 
the  class  may  be  only  transitory,  as  in  whales  and 
some  thick-skinned  animals,  or  the  hairs  may  be 
thick  and  spine-like,  as  in  the  porcupine  and  hedge- 
hog, or  they  may  be  united  into  scales,  as  in  the 
manis  and  armadillo,  or  on  the  tail  of  a  rat.  Each 
hair  is  the  epidermal  secretion  of  a  single  papilla,  and 
is  a  solid  cylinder  composed  of  long  cortical  or  super- 
ficial cells,  and  rounder  central  cells.  The  hairs  arise 


Skeleton  of  Mammalia.  75 

in  pits  or  follicles,  and  into  these  follicles  there  open 
sebaceous  glands,  which  secrete  an  oily  material  for 
the  lubrication  of  the  hairs. 

The  neck-region  of  the  vertebral  column  or  back- 
bone in  all  mammals  consists  of  seven  vertebrae, 
except  in  three  cases;1  the  back  region  consists  of 
about  twenty,  but  the  number  is  more  variable;  the 
shoulder  girdle  is  never  connected  directly  to  the 
spine,  but  the  pelvic  girdle  always  is  so,  and  hence 
there  are  always  certain  vertebrae  thickened  and  united 
for  the  purpose  of  supporting  the  pelvis;  these  are 
"known  as  the  sacrum,  and  behind  this  in  most 
mammals  is  the  tail,  which  varies  extremely  in  length, 
sometimes,  as  in  the  long-tailed  manis  of  Western 
Africa,  having  over  forty  vertebrae,  in  others,  as  in 
some  bats,  having  only  three.  In  man  there  are  four 
very  small  rudimental  tail  vertebrae,  and  the  same 
number  exists  in  the  gorilla,  chimpanzee,  and  orang- 
outang. In  many  mammals,  as  the  South  American 
monkeys,  opossums,  and  kinkajous,  the  tail  is  prehen- 
sile and  is  used  as  an  additional  hand  in  climbing. 

50.  Skeleton. — The  skeleton  consists  of  two  classes 
of  bones,  some  with  an  interior  of  spongy  cells,  others 
with  an  internal  cavity.  In  both  cases  the  hollow 
spaces  are  filled  with  marrow.  The  skull  in  mammals 
is  a  solid  box  to  which  the  upper  jaw  is  immovably 
fixed,  and  it  articulates  with  the  first  vertebra  of  the 
neck  by  means  of  two  articular  knobs  or  condyles. 
The  lower  jaw  is  composed  of  two  pieces  only,  one 
on  each  side,  and  it  forms  a  joint  directly  with  the 

1  These  are  two  sloths,  one  having  9,  the  other  6  vertebrae, 
and  an  aquatic  American  animal,  the  manatee,  which  has  6. 


76  Vertebrata. 

skull,  beneath  the  ear.  The  shape  of  the  articular 
surfaces  which  form  this  joint  is  variable,  and  de- 
pends on  the  nature  of  the  food  and  the  character  of 
the  motions  which  are  necessary  for  mastication. 
Thus,  in  flesh-eating  animals  the  lower  jaw  has  a 
transversely  elongated,  cylindrical  condyle,  which  can 
allow  only  of  a  vertical  motion,  while  in  gnawing 
animals  the  lower  jaw  slides  forwards  and  backwards. 
51.  Teeth. — The  jaw  arches,  and  they  alone,  bear 
teeth,  which  are  arranged  in  one  row  ;  no  accessory 
teeth  are  developed  on  the  palate  as  in  reptiles  and 
fishes.  The  teeth  are  always  in  sockets,  and  are 

FIG.  34. 


Skull  of  anteater,  a  perfectly  toothless  mammal. 

rarely  absent,  as  in  the  ahteaters  (fig.  34),  though 
sometimes  they  are  rudimental  and  disappear  early, 
as  in  whales.  There  are  usually  two  sets  of  teeth  ; 
one  an  early  developed  or  milk  set,  which  soon  drop 
out  and  are  succeeded  by  a  second  or  permanent  set ; 
thus  reminding  us  of  what  we  found  in  crocodiles, 
where  successively  growing  teeth  follow  each  other  in 
the  one  row  almost  indefinitely  as  long  as  growth 
continues.  Those  teeth  in  the  upper  jaw  which  are 
rooted  in  the  foremost  bone,  or  premaxilla,  are  called 
incisor  teeth,  and  have  usually  a  cutting  edge  and  a 
single  root.  When  the  first  tooth  in  the  maxilla  or 
jaw  proper,  is  placed  near  the  suture  or  line  of  con- 
tact between  that  bone  and  the  premaxilla,  it  is 


Teeth  of  Mammals.  77 

generally  long  and  pointed  and  has  but  one  root 
To  it  the  name  canine  is  given,  while  the  other 
maxillary  teeth  have  in  general  two  or  more  fangs, 
and  are  called  grinding  teeth  or  molars.  The  milk 
teeth  are  usually  fewer  than  the  permanerft  teeth,  and 
hence  some  of  these  grinders  have  had  predecessors 
while  others  have  not ;  those  which  are  secondary 
are  called  premolars,  while  those  which  are  primary 
(the  hindermost),  are  called  molars.  Similar  names 
are  given  to  the  corresponding  teeth  in  the  lower  jaw. 
As  the  teeth  vary  in  number  and  size  in  the  different 
orders  of  mammals,  they  afford  a  good  and  easy 
system  whereby  the  different  forms  can  be  discrimi- 
nated ;  and  in  order  to  be  able  briefly  to  describe  the 
characteristic  dentition  of  any  animal,  zoologists  are 
in  the  habit  of  tabulating  the  number  and  arrange- 
ment of  the  teeth  of  animals  in  a  set  formula  :  thus 


FIG.  35. 


Teeth  of  Tasmanian  devil. 

to  write  the  dental  formula  of  an  animal  we  first  put 
down  the  initials  of  the  sets  of  teeth,  and  follow  each 
initial  by  the  number  of  teeth  of  that  sort  in  the  two 
jaws,  those  of  the  upper  jaw  being  written  like  the 


78  Vertebrata. 

numerator  of  a  fraction,  while  those  of  the  lower  are 
placed  as  the  denominator;  thus,  in  an  adult  man 

the  dental  formula  is  /-— ,  C^=±,  P^^,  M^^ ; 
2—2       i— i       2—2        3—3' 

that  is,  on  each  side  of  each  jaw  there  are  two  in- 
cisors, on  each  side  of  each  jaw  one  canine,  two  pre- 
molars,  and  three  molars.  The  jaws  are  almost 
always  protected  by  fleshy  lips,  except  in  the  first 
order. 

52.  Viscera. — Mammals  have  well  developed 
brains,  and  usually  acute  sense-organs.  The  lungs 
and  heart  are  separated  from  the  intestine  and  other 
digestive  organs  by  a  muscular  partition,  called  the 
diaphragm,  which  is  an  important  agent  in  breathing. 
The  heart  consists  of  four  cavities,  and  the  opening 
between  the  right  auricle  and  right  ventricle  is  guarded 
by  a  membranous  valve  consisting  of  three  flaps. 
There  is  but  one  aortic  arch  in  the  adult,  and  it 
arches  to  the  left  side  ;  there  are  two  carotid  arteries 
for  conveying  blood  to  the  brain.  The  blood  con- 
tains round,  non-nucleated  corpuscles,  and  therein 
differs  from  that  of  any  of  the  foregoing  classes. 

There  are  seventeen  orders  of  mammals  at  pre- 
sent living,  but  representatives  of  several  additional 
and  most  remarkable  intermediate  orders  have  been 
found  in  a  fossil  state,  especially  in  the  tertiary  beds 
in  America. 


79 
CHAPTER  XV. 

CLASSIFICATION   OF  MAMMALS. 

53.  Order   1,  Monotremata. — The  first  order  of 
mammals  is  called   Monotremata,  and   includes   two 
remarkable  Australian  forms,  the  platypus   and   the 
spiny  anteater.     They  are  both  small  animals,  being 
about  a  foot  in  length.     Both   have   long   coracoid 
bones  separate  from  the  shoulder-blade  or  scapula, 
which,  bird-like,  reach  as  far  as  the  sternum,  and  the 
two  collar-bones  unite  into  a  single  T-shaped  merry- 
thought-like bone.     In  both  forms  there  are  two  long 
spur-like  bones  articulated  to  the  front  of  the  pelvis 
and  embedded  in  the  abdominal   muscles,   and   in 
both  the  bones  of  the  skull  unite  at  an  early  period 
to  form  a  perfectly  continuous  braincase.     They  are 
also   characterised    by   the    intestine   and    excretory 
organs    opening,   as   in   the   birds,   into  a   common 
cloaca  (hence  the  name  of  the  order).     The  platypus, 
or  OrnithorhynckuSy  is  aquatic,  and  has  a  duck-like 
bill  and  two  small,  flat,  horny  teeth  in  each  jaw.    The 
male  has  a  strong  hollow  spur  on  the  ankle  which 
communicates  with  the  duct  of  a  poison  gland  and 
is   a   weapon   of   offence.      The   spiny   anteater,   or 
Echidna  (fig.  36),  is  toothless,  and  has  a  long  slender 
horny  bill,  a  worm-like  tongue,  and  a  dermal  covering 
of  strong  stout  spines.    The  young  of  both  these  forms 
are  born  in  a  very  imperfect  state  of  development 

54.  Order  2,  Marsupialia. — The  second  order  of 
mammals  is  named  Marsupialia,  and  includes  kanga- 


8o 


Vertebrata. 


roos  and  opossums,  and  all   those   other  Australian 
forms  in  which  the  females  bear  on  the  under  surface 


Kangaroos. 


81 


of  the  body  a  pouch  wherein  the  young  are  received 
and  sheltered  after  their  birth.  This  pouch  is  sup- 
ported by  two  bones  (fig.  37,  ///,)  FIG.  37. 
similar  to  those  described  in 
connection  with  the  pelvis  of 
the  Monctremes ;  to  these  bones 
the  name  marsupial  bones  has 
been  given,  but  they  exist  in  the 
pouchless  males  as  well  as  in 
the  pouch-bearing  females.  All 
the  marsupials  are  clad  with 
thick  fur,  and  they  are  armed 
with  claw-bearing  toes,  two  of 
which  on  the  hind  foot  tend 
to  become  very  small  and  united 
within  a  common  web  of  skin. 
They  exhibit  many  characters 
of  inferiority  to  the  other  mam- 
mals ;  thus  the  two  lateral  lobes 
of  the  fore -brain  are  nearly 
smooth  on  the  surface  and  are 
imperfectly  united  together,  and  the  young  are  born 
in  an  exceedingly  rudimental  state. 

The  marsupials  vary  very  much  in  habit,  and  are 
modified  to  suit  these  habits.  Thus,  the  Tasmanian 
devil  and  Tasmanian  wolf  are  flesh-eaters,  with  sharp 
claws  and  sharp  strong  teeth  (fig.  35).  The  opossums 
of  America  are  insect-eaters,  and  have  sharp  and 
numerous  teeth  ;  they  are  the  only  marsupials  which 
live  outside  the  great  Australian  region,  to  which 
all  the  others  are  confined,  and  of  which  they  are 
almost  the  sole  mammalian  inhabitants.  Some  of 

G 


Pelvis  of  kangaroo, 
marsupial  bones;  62,  ilium. 


82 


Vertebratd. 


ftie  opossums  have  the  pouch  rudimental,  and  the 
mother  carries  her  young  ones  on  her  back,  often 


with  their  prehensile  tails  coiled  round  her 
tail.  Others,  like  the  yapock  of  South 
America,  are  amphibious,  and  have  webbed 
feet 

The  kangaroos  proper  (fig.  38)  are 
characterised  by  the  enormous  dispropor- 
tion of  the  fore  and  hind  limbs  ;  the  former 
are  short,  five-fingered,  while  the  latter 
are  very  long  with  long  feet,  the  middle  or 
third  toe  (which  corresponds  to  our  fourth, 
as  they  have  no  great  toe)  being  enormous 
in  length,  the  fourth  being  a  little  smaller, 
while  the  first  and  second  are  united  and  excessively 


Kangaroos,  Phalangers.  83 

slender.  The  tail  is  thick  and  with  the  hind  legs 
makes  a  tripod  whereupon  the  animal  rests  when 
standing.  In  feeding,  the  animal  bends  down  so  as 
to  rest  on  the  short  forepaws,  and  in  running  it  pro- 
gresses by  a  series  of  long  leaps  or  bounds  in  which 
it  uses  only  its  hind  legs. 

The  largest  living  kangaroos  are  about  five  to  six 
feet  high  when  standing ;  but  the  majority  of  the 
species  are  small,  some  being  not  larger  than  a  rat 

FIG.  39. 


Teeth  of  kangaroo  rat. 

These  true  kangaroos  are  herbage -feeders,  and  they 
have  a  complexly-pouched  stomach  to  enable  them  to 
digest  green  food.  Their  teeth  generally  are : — 


The  phalangers,  or  Australian  opossums,  are  fruit- 
eaters  for  the  most  part,  and  like  the  opossums  of 
America  they  have  an  opposable  thumb  on  the  hind 
foot,  which  thus  is  able  to  act  in  grasping  like  a  hand. 
Some  of  these  phalangers  have  wing-like  side  folds  of 
skin  stretching  from  the  fore  to  the  hind  limbs,  where- 
by they  are  able  to  take  long  flying  leaps. 


84  Vertebrata. 

The  wombat  is  a  burrowing  and  gnawing  mar- 
supial, whose  chisel-shaped  incisor  and  other  teeth 
continue  permanently  to  grow,  and  thus  the  waste  of 
tooth-tissue  which  takes  place  in  the  process  of  grind- 
ing the  roots  and  twigs  which  constitute  its  food,  is 
restored.  This  animal  is  about  2\  feet  long,  and,  like 
the  koala  or  native  bear  of  Australia,  has  an  accessory 
gland  in  the  stomach,  and  a  long  caecum  or  pouch, 
where  the  large  and  small  intestines  unite.  They  are 
both  also  almost  tail-less,  and  the  koala  has  its  thumb 
and  index  fingers  capable  of  being  opposed  to  the 
others. 

Some  fossil  kangaroos,  like  the  Diprotodon,  were  of 
great  size ;  one  thigh  bone  of  this  animal  in  the  museum 
of  the  University  of  Dublin,  must  have  been  at  least 
two  feet  in  length  when  complete.  It  is  also  interesting 
that  the  earliest  fossil  mammals  which  have  as  yet  been 
discovered  are  marsupials.  The  bones  of  marsupials 
are,  in  general,  easily  recognised ;  thus  the  lower  jaw 
has  an  inflexed  angle,  whereby  it  can  be  distinguished 
from  that  of  any  other  mammal.  The  dentitions  of 
marsupials  are  very  variable,  as  can  be  seen  from  the 
four  subjoined  examples  : — 


Kangaroo  (fig.  37) 


— *    /i^4— 4 


i — i 


Myrmecobius   or)  74~ 4  rI~I    p2~2    *f5—5 
banded  anteater)      3—3'      i— i'      3—3'      6—6' 

Tasmanian   devil)  r4 — 4  ri — i    P2 — 2    ,,-4 — 4 
(fig.  35)         J3^3       i=?^J=?. '   4=? 


CHAPTER  XVI. 

PLACENTAL   MAMMALS. 

55.  The  Placenta. — In  all  the  succeeding  orders 
of  mammals  the  young  are  not  born  until  their 
internal  organisation  has  become  much  more  perfectly 
developed  than  in  the  case  of  the  young  of  the  mar- 
supials and  monotremes ;  and  in  order  to  provide  for 
their  nutrition  while  they  are  thus  growing,  a  peculiar 
vascular  organ,  called  the  placenta,  is  developed, 
whereby  blood  is  supplied  to  the  embryo  for  its 
nourishment;  hence  they  are  called  placental  mam- 
mals to  distinguish  them  from  the  marsupials,  which 
are  named  non-placental  mammals. 

Order  3,  Edentata. — The  third  mammalian  order 
is  known  as  Edentata^  and  includes  the  anteaters  and 
armadillos,  which  are  easily  recognised  by  the  absence 
of  incisor  teeth,  at  least  in  the  middle  of  the  jaws,  so 
that  the  front  of  the  long,  snout-like  mouth  appears 
toothless,  hence  the  name.  They  are  all  armed  with 
strong,  usually  sharp  claws,  and  are  clad  with  coarse 
hair,  or  else  with  hard  scales,  and  feed  on  insects, 
small  animals,  or  carrion.  The  true  anteaters  are 
natives  of  South  America,  and  are  quite  toothless  (fig 
34).  They  have  exceedingly  long,  worm-like  tongues, 
which  they  can  protrude  for  the  purpose  of  entrap- 
ping the  insects  whereon  they  feed  ;  and  they  have 
an  enormous  pair  of  glands  in  the  neck  which  secrete 
a  glutinous  fluid  to  render  the  surface  of  the  tongue 
sticky.  This  long  tongue  they  can  retract  rapidly, 


86 


Vertebrata. 


FIG.  40. 


and  in  order  to  enable  them  to  accomplish  this,  the 
retractor  muscle  extends  back  to  the  hinder  end  of 
the  breast-bone,  which  itself  is  often  enormously 
elongated.  Some  anteaters  are  over  five  feet  in 

length,  others  are  much 
smaller.  The  great  Cape 
anteater  of  South  Africa 
is  closely  allied,  but  has 
a  strap-like  tongue  and 
grinding  teeth,  which  are 
peculiar  in  their  struc- 
ture, as  each  tooth  con- 
sists, not  of  a  single 
papilla  like  the  teeth  of 
most  other  animals,  but 
of  a  closely  united  bundle 
of  separate  papillae  (fig. 
40).  The  pangolins  of 
Africa  and  Asia  are 
covered  with  overlap- 
ping epidermal  scales, 
and  are  also  toothless 
\W3W  and  insect-eaters.  They 

Tooth  of  Orycterope  or   Cape  Ant-    all  have  CHOrmOUS  claWS 
eater  magnified,  showing  the  sepa-  ...          , 

•ate  papiii^,/,  of  which  each  tooth  on  their  hands  for  tear- 
is  made  up  ;  d,  dentine,  or  tooth-     «  ,  •,  i  -11 
substance  ;  c,  cement.                          mg  Open  the  ant-hills  SO 

as  to  reach  their  prey. 

The  second  family,  or  the  armadillos,  are  South 
American,  scale-covered  burrowing  animals,  with 
grinding  teeth  and  a  short  tongue.  They  feed  chiefly 
on  carrion  or  small  animals,  and  their  dermal  armour 
is  arranged  in  transverse  girdles  or  bands  which  may 
be  movable  on  each  other. 


A  rmadillos.  87 

The  Edentates  now  existing  are  all  of  moderate 
or  small  size,  but  from  the  remains  of  fossil  forms  we 


know  that  some  of  them  must  have  been  of  gigantic 
proportions. 


88 


Vertebrata. 


56.  Order  4,  Bradypoda,  or  Sloths. — These  are 
tail-less   animals   inhabiting   South  America.     They 


are  often  united  with  the  Edentates,  from  which  they 


Sloths  and  Manatees.  89 

differ  in  the  possession  of  short  round  heads,  not  pro- 
longed into  a  snout,  with  a  lower  jaw  of  one  piece, 
even  from  a  very  early  age,  and  also  by  having  a  very 
remarkable  down-directed  process  of  the  malar  or 
cheek-bone.  They  are  strictly  vegetable-feeders,  and 
have  sacculated  stomachs.  Their  whole  organisation 
is  adapted  to  an  arboreal  life,  and  they  live  suspended 
from  the  branches  of  trees  by  their  long  and  strong 
hook-like  claws.  They  are  clad  with  coarse  hair  of 
a  dirty  white  or  brownish  colour,  and  have  two  or 
three  toes  only.  The  peculiarity  of  their  neck  verte- 
brae has  been  alluded  to  before  (§  49).  They  have  no 

incisor  teeth  and  ^—^-  molars,  which  are  simple  and 

nearly  flat-topped. 

The  Megatherium,  a  fossil  sloth  from  South 
America,  must  have  been  little  less  in  size  than  a 
large  hippopotamus.  In  many  respects  it  and  its 
allies  seem  like  passage  forms  from  the  sloths  to  the 
armadillos. 

57.  Order  5,  Sirenia  or  Manatees,  constitute  a 
small  group  of  sea-weed-eating  marine  animals,  of  a 
somewhat  fish-like  habit  and  form,  usually  found  near 
the  mouths  of  rivers.  They  have  a  thick  skin,  sparsely 
covered  with  bristles,  and  flat-crowned  grinding  teeth. 
They  have  no  hind  limbs,  and  the  fore-limbs  are 
converted  into  paddles.  The  heart  in  some  is  deeply 
cleft,  the  right  and  left  ventricles  being  nearly  separate 
from  each  other  (fig.  43).  One  animal  of  this  group, 
the  Rhytina,  which  inhabited  some  islands  in  Behring's 
Strait,  has  become  extinct  within  the  last  century. 
Another,  the  dugong,  inhabits  the  Indian  Ocean, 


QO  Vertebrata. 

while  the  manatee  or  mermaid  is  a  native  of  the 
opposite  shores  of  the  South  Atlantic,  extending  from 
South  America  to  Africa.  These  are  often  confounded 
with  whales,  but  can  be  known  therefrom  by  their 


FIG.  43. 


Heart  of  dugong,  showing  the  separation  of  the  ventricles. 

n,  right  auricle  ;  d,  left  auricle  ;  b,  right  ventricle ;  e,  left  ventricle  ; 
f,  aorta  ;  c,  pulmonary  artery. 

possessing  a  neck,  a  movable  elbow-joint,  a  trace  of 
nails,  and  nostrils  far  forward  and  not  at  the  top  of 
the  head.  They  also,  except  the  extinct  Rhytina, 
possess  teeth. 

58.  Order  6,  Ungulata,  includes  all  those  herbi- 
vorous mammals  whose  extremities  are  used  solely  as 
organs  of  progression,  and  not  of  prehension,  and  in 
which  each  toe  ends  in  a  hoof  or  broad  case  of  horny 
epidermis.  They  are  usually  animals  of  large  size, 
and  they  have  no  collar-bones.  Their  brains,  however, 
are  small  in  proportion  to  the  bulk  of  the  body,  and 


Horse,  Ass,  and  Tapir.  91 

the  intestinal  canal  is  of  very  great  length.  There  are 
two  chief  sub-orders  of  these  hoofed  animals,  the  first 
consisting  of  such  as  have  odd  toes  on  their  hind 
feet,  and  unsymmetrical  toes  on  the  fore  feet.  Of 
these  odd-toed  mammals,  there  are  three  living 
types—  horses,  tapirs,  and  rhinoceroses.  The  horse 
and  ass  have  only  a  single  toe  developed  on  each 
limb,  which  corresponds  to  the  third  toe  of  ordinary 
mammals.  They  have  also  a  dentition  of 


,9 

6       i—  i       4—4        3—3 

The  two  best  known  forms  are  the  horse  and  the 
ass  ;  the  former  is  characterised  by  its  tail,  hairy  from 
its  base,  and  by  the  wart-like  callosities  on  the  inner 
surface  of  its  legs.  Remains  of  horses  are  found  in 
the  bone  caves  of  Britain  and  of  South  America,  as 
well  as  in  those  of  Continental  Europe.  The  striped 
races  of  the  genus  Equus  are  confined  to  Africa  ;  they 
are  the  zebra,  the  quagga,  the  dauw,  &c.,  and 
are  scarcely  tameable.  The  wild  asses  inhabit 
Western  Asia,  Fossil  horses  are  known,  exhibiting 
all  the  intermediate  grades  of  development  of  feet 
from  the  single  hoof  of  the  common  horse  to  the 
Eohippus  with  four  functional  toes  and  a  fifth  rudi- 
mentary one  on  the  fore  feet,  and  three  toes  behind. 

The  tapirs,  natives  of  Malaya  and  of  South  America, 
are  also  uneven-toed  ungulates,  possessing  three  toes 
on  their  hinder,  and  four  (but  laterally  unsymmetrical) 
toes  on  their  fore  feet  They  are  characterised  by 
possessing  a  proboscis-  like  snout,  and  rather  long 
legs.  In  number  the  teeth  are  equal  to  those  in  a 
horse. 


92  Vcrtebrata. 

The  rhinoceros  (fig.  44)  is  the  third  type  of  this 
sub-order,  and  is  a  native  of  Africa  and  the  Malay 


/ 


/-' 


archipelago;  the  foot  is   three-toed,  and  the  skin  of 


Rhinoceros,  Swine.  93 

enormous  thickness  and  often  folded.  The  leading 
characteristic  is  the  long  epidermal  horn  which  is 
rooted  in  the  dermis  on  the  upper  surface  of  the  nose. 
This  in  structure  consists  of  a  tuft  of  confluent  hairs, 
and  sometimes  grows  to  several  feet  in  length,  and  is 
of  great  hardness;  the  horn  is  always  medial,  and 
usually  single,  when  two  exist  they  are  placed  one  in 
front  of  the  other.  At  one  time  a  species  of  rhino- 
ceros clothed  with  a  woolly  coating  inhabited  Great 
Britain  and  the  northern  parts  of  Europe  and  Asia, 
but  it  became  extinct  in  prehistoric  times. 

All  these  odd-toed  ungulates  have  at  least  twenty- 
two  vertebrae  in  their  trunk,  interposed  between  the 
neck  and  the  sacrum,  and  they  all  have  a  bony  knob 
or  third  trochanter  on  the  outside  of  the  shaft  of  the 
thigh  bone  for  the  attachment  of  muscles.  See  fig. 
44,  also  fig.  41. 

The  second  sub-order  of  hoofed  animals  includes 
those  whose  toes  are.  in  even  numbers,  two  or  four, 
and  are  laterally  symmetrical  (when  there  are  four, 
two  are  in  front  and  two  behind).  They  have  for  the 
most  part  nineteen  dorso-lumbar  vertebrae,  and  none 
of  them  have  the  protuberance  on  the  thigh-bone 
referred  to  above.  Many  of  them  have  horns,  but 
these  are  always  on  the  forehead,  and  one  on  each 
side,  never  median  as  in  the  rhinoceros. 

59.  Swine  and  Hippopotami. — There  are  two  very 
well-marked  divisions  of  these  even-toed  ungulates. 
In  one  of  these  the  animals  have  simple  stomachs, 
and  the  grinding  teeth  have  little  knobs  or  protuber- 
ances on  their  surfaces,  hence  these  are  called  Buno- 
donts  j  in  the  other  group  the  stomachs  are  complex, 


94  Vertebrata. 

and  the  hardest  layer  of  the  teeth  (the  enamel),  is 
arranged  in  crescents;  these  are  known  as  Ruminants. 
FIG  Of  the  btmodonts  the  pigs  are  the 

most  familiar  examples.     Our  domes- 
tic pigs   are  derived  from  the  wild 
boars  of  Southern  Europe  and  Asia, 
animals    which    formerly    inhabited 
Great  Britain  in  a  wild  state.     The 
babyroussa  of  the  Malay  Islands  is 
Crown  of  the  tooth  of  a  singular  pig  whose  upper  canine 
Lfmeericsre°s±fs.the  teeth  grow  upwards  and  arch  back- 
wards so  as   to  reach   the  forehead 
where  they  end  in  a  curled  point.     Most  of  the  pigs 
have  large  tusk-like  canines,  and  their  teeth  are  usually 
represented  by  the  formula 


3—3       i  -i       3—3        3—3 

The  hippopotamus  of  the  rivers  of  Africa  is  an 
enormous  pig-like  creature,  with  very  short  legs  and 
a  heavy  body,  and  with  long  tusk-like  incisors,  two  in 
each  jaw  ;  it  sometimes  reaches  a  length  of  nine  feet. 
60.  Ruminants.  —  The  ruminants  are  so  called 
because  they  chew  the  cud,  that  is,  they  subject  their 
food  to  a  second  chewing  after  it  has  been  swallowed. 
They  are,  for  the  most  part,  large  soft-fleshed  animals, 
the  favourite  prey  of  large  carnivores,  and  as  the  food 
which  they  require  for  their  nourishment  is  bulky, 
being  green  herbage,  and  only  to  be  obtained  in  open 
places  of  pasturage,  where  they  would  be  exposed 
without  shelter  to  the  assaults  of  their  enemies,  it 
becomes  a  matter  of  vital  importance  for  their  well- 


Stomachs  of  Ruminants. 


95 


being  that  the  process  of  mastication,  a  long  and 
tedious  one  in  the  case  of  such  food,  should  be  kept 
over  until  the  animal  has  laid  in  its  store  of  provisions 


and  retired  to  a  sheltered  hiding-place.     Accordingly 
the  stomach  of  a  ruminant  is  divided  into  four  com- 


g6  Vertebrata. 

partments,  and  into  the  first  of  these  (called  the 
paunch}  the  food  is  taken  when  first  swallowed  ;  then 
it  passes  into  the  second  division,  which  consists  oi 
many  large  hexagonal  cells  or  little  chambers ;  here 
it  becomes  divided  into  masses  for  re-chewing,  and 
these  pass  up  the  oesophagus  back  into  the  mouth, 
where  it  is  carefully  and  slowly  masticated,  and  mixed 
with  saliva,  after  which  it  is  re-swallowed,  but  this  time 
as  a  semi-fluid  soft  material,  which  on  reaching  the 
stomach  is  conducted  along  a  gutter  made  by  a 
mucous  fold,  into  the  third  stomach  or  liber,  which 
consists  of  many  layers  of  mucous  membrane  arranged 
like  the  leaves  of  a  book.  Here  the  materials  are  still 
farther  mixed  up  with  the  secretions  of  gastric  glands, 
and  pass  on  into  the  fourth  stomach,  where  digestion 
finally  takes  place.  The  camels  of  Arabia  and  Africa 
differ  from  the  other  ruminants  in  having  no  third 
stomach,  in  possessing  canine  teeth  in  each  jaw,  and 
two  lateral  incisor  teeth  in  the  upper  jaw.  They  have 
also  nails  rather  than  hoofs  on  their  large  and  well- 
padded  toes.  The  hump  on  the  camel's  back  consists 
of  fat  and  cellular  tissue.  There  is  a  single  hump  on 
the  dromedary,  but  there  are  two  on  the  back  of  the 
Arabian  or  Bactrian  camel.  The  second  stomach  of 
the  camel  has  deep  cells  or  compartments,  which  has 
given  origin  to  the  fables  about  the  capacity  of  camels 
to  store  water  in  their  stomachs. 

The  llamas  of  the  Andes  in  South  America  are 
closely  allied  to  the  camels,  and  agree  with  them  in 
most  of  their  peculiarities,  but  have  no  humps.  The 
musk-deer,  which  inhabit  the  mountainous  regions 
between  the  Himalaya  and  the  Altai  mountains,  have 


The  Cow. 


97 


also    canine    teeth,  and    are    distinguished    by  the 
presence  of  a  pair  of  odour-secreting  musk-glands. 


98  Vertebrata. 

The  other  ruminants  have  neither  canine  nor 
incisor  teeth  in  the  upper  jaw,  and  most  of  them 
possess  horns.  In  the  giraffe,  the  tallest  and  longest- 
necked  of  the  mammals,  these  horns  are  short  pro- 
cesses of  the  frontal  bone  covered  with  hairy  skin. 
In  the  cows,  antelopes,  goats  and  sheep,  these  horns 
are  made  up  of  an  outer  hard,  horny  sheath,  placed 
over  a  bony  core  or  process  of  the  frontal  or  forehead 
bone.  In  the  ox  and  cow  group,  the  horns  are 
directed  forwards,  and  are  smooth,  while  in  the 
antelopes,  which  are  mostly  natives  of  Africa,  the 
horns  are  directed  backwards,  and  are  often  ringed 
or  waved.  One  American  species,  the  pronghorn, 
sheds  its  horns  periodically  like  the  true  deer.  The 
goats  and  sheep  have  compressed  angular  wrinkled 
horns,  often  coiled.  Our  domestic  sheep  are  possibly 
derived  from  the  mountain  sheep  of  South  Europe 
and  Asia. 

The  deer  family  possess  solid  horns  composed  of 
bony  processes  of  the  frontal  bone,  often  branched  in 
various  ways.  These  antlers  are  annually  shed  and 
renewed,  each  new  growth  being  usually  larger  than 
its  predecessor.  The  best  known  examples  are  the 
Virginian  deer,  the  fallow  deer,  and  the  roebuck. 
In  most  of  these  ruminants  the  dentition  is  repre- 
sented by  the  formula 


/2-o      ^-o       3-3 

3—3       i—  i      3—3       3—3 


99 


CHAPTER    XVII. 

CLASSIFICATION   OF   MAMMALS — continued. 

6 1.  Order  7,  Cetacea  (Whales).— These,  like  the 
Sirenia,  are  marine  mammals  with  no  hind  limbs,  and 
having  the  fore  limbs  converted  into  fins.  They  are 
fish-like  in  shape,  without  necks,  and  have  a  smooth 
thick  skin  beneath  which  is  a  thick  layer  of  fat  known 
as  blubber.  The  nostrils  are  situated  on  the  upper 
surface  of  the  head,  and  are  called  blow-holes,  and 
are  well  protected  by  dermal  folds  so  as  to  prevent 
the  entrance  of  water  into  the  air-passages  while 
the  whale  is  beneath  the  surface  of  the  sea.  These 
animals  require  to  rise  to  the  surface  to  breathe,  and 
on  doing  so  they  forcibly  eject  a  shower  oi  spray, 
consisting  of  the  mucus  secreted  by  the  membrane  of 
the  nasal  passages,  the  vapour  of  the  breath,  and 
whatever  sea  water  lurks  in  the  crevices  about  the 
nostril ;  this  process  is  called  blowing,  and  it  is  in 
reality  somewhat  like  a  forcible  sneeze  preparatory  to 
a  deep  inspiration.  The  sense  of  smell  is  almost  or 
altogether  absent.  There  are  seven  cervical  vertebrae, 
but  they  are  usually  united  together  so  as,  in  old 
whales,  to  form  one  bone. 

The  tail  in  whales  consists  of  two  lateral,  hori- 
zontally-placed lobes  consisting  of  folds  of  skin  and 
connective  tissue  appended  to  the  end  of  the  vertebral 
column  ;  this  is  the  chief  instrument  of  locomotion. 

The  mouth  in  true  whales  is  of  enormous  capacity, 
and  as  theii  food  is  mostly  small  fish,  cuttlefishes  and 


ioo  Vertebrate. 

molluscs,  they  require  to  take  in  very  large  quantities 
of  this  material  for  their  nourishment,  which  they  do 
in  the  following  way.  The  jaw  arches  are  covered  all 
around  their  edges  with  horny  plates  of  *  whalebone,' 
fringed  with  bristles  in  place  cf  teeth,  and  these  act 
as  strainers.  In  feeding,  the  animal  opening  its  mouth, 
takes  in  a  mouthful  of  sea-water  and  its  animal 


FIG.  48. 


Head  and  tongue  of  whale. 
a,  tongue  (represented  much  too  large)  ;  b,  whalebone  plates. 

contents,  and  then  by  closing  the  jaws  and  pressing 
the  tongue  against  the  palate,  expels  the  water  through 
the  slits  between  the  whalebone  plates,  which  by  their 
opposition  and  by  their  bristly  margin  retain  the  solid 
materials  to  be  subsequently  swallowed. 

In  some  whales  there  are  exceedingly  minute 
rudiments  of  the  hind  limbs,  in  the  form  of  small 
ischia  or  pelvic  bones,  embedded  in  the  muscles  of 
the  abdomen,  and  not  visible  on  the  surface. 

Whales  have  usually  complex  stomachs,  often 
with  four  chambers;  they  have  also  a  moderately  long 
alimentary  canal,  large  and  tortuous  networks  of  blood- 
vessels along  the  ribs,  and  a  thick  fleshy  diaphragm. 


Seals  and  Walruses.  101 

The  large-headed  sperm  whales  are  often  as  much 
as  sixty  to  eighty  feet  long.  One  third  of  the  whole 
length  is  formed  by  the  head,  whose  anterior  bones, 
enormously  dilated,  are  hollowed  into  a  chamber 
which  contains  the  substance  called  spermaceti,  used 
in  making  ointments  and  cosmetics.  These  whales 
possess  from  fifty  to  sixty  large  conical  teeth  in  the 
lower  jaw,  and  therein  differ  from  the  baleen  whales, 
which  in  some  cases  possess  small  embryonic  teeth 
that  disappear  early  and  are  replaced  by  the  whale- 
bone plates.  The  common  porpoises,  bottle-noses, 
and  dolphins  have  numerous  simple  teeth  in  both 
jaws,  and  the  narwhal  has  one  enormous  front  tooth 
which  sometimes  grows  to  a  length  of  5^  or  6  feet, 
forming  a  horizontal  tusk.  Whales  are  the  largest  of 
animals,  and  have  been  seen  over  ninety  feet  in 
length. 

62.  Order  8,  Pinnipedia. — This  small  order  con- 
sists of  the  seals  and  walruses,  and  forms  a  connecting 
link  between  the  whales  on  the  one  hand  and  the  bears 
on  the  other.  They  are  aquatic,  fish-eating,  hair-clad 
mammals,  with  four  fin-like  limbs,  each  provided  with 
five  webbed  digits.  The  hind-limbs  are  stretched 
horizontally  backwards  on  the  same  line  as  the  tail, 
to  which  they  are  very  closely  united.  They  have 
roundish  heads  provided  with  numerous  sensitive 
bristles,  large  eyes,  and  loosely  united  facial  bones. 
They  have  valvular  nostrils,  no  external  ears,  simple 
stomachs,  and  large  venous  cavities  to  hold  the 
impure  blood  while  respiration  is  suspended  during 
diving. 

Most  seals  are  marine,  but  some   live  in  fresh- 


IO2  Vertebrate 

water  lakes  as  in  Lake  Baikal.  Our  common  seal  is 
inoffensive  and  easily  tamed.  The  walrus,  known  by 
its  huge  tusks  or  canine  teeth,  used  for  digging  up 
the  molluscs  on  which  it  feeds,  sometimes  reaches 
twenty  feet  in  length.  The  fur  seals,  whose  beautiful 
sk  ns  are  of  such  commercial  importance,  are  natives 
of  the  Southern  Atlantic  and  Pacific  Oceans.  The 
dentition  of  the  common  seal  is 


2  -  2          I—  I          3  -  3  2  -  2 

63.  Order  9,  Carnivora.  —  The  flesh-eating  mam- 
mals are  the  cats,  dogs,  weasels  and  bears,  known  by 
possessing  sharp  claws,  long  pointed  canine  teeth,  a 
simple  stomach,  and  a  short  intestine.  The  lower 
jaw  is  constructed  to  move  only  in  the  vertical  plane 
up  and  down,  having  no  lateral  motion,  the  condyle 

FIG.  49. 


Skull  of  lion. 
7,  median  temporal  crest ;  12,  post-orbital  process ;  15,  nasal  bone. 

being  transversely  lengthened.     The  molar  teeth  are 
ridged  and  sharp,  so  as  to  be  fitted  for  dividing  flesh. 


Cats,  Dogs,  Lions.  103 

They  never  have  collar-bones.  The  skull  of  a 
carnivore  can  be  easily  known  by  the  prominent 
medial  crest  for  the  attachment  of  the  powerful 
muscles  which  move  the  lower  jaw  (fig.  49,  7). 

The  dog  is  a  typical  carnivore,  whose  teeth  are 
represented  by  the  formula 


3—3       i—  i       4—4       3—3 

In  progression  dogs  are  digitigrades,  that  is  they  only 
rest  on  the  last  joint  of  their  toes  in  walking,  and 
their  claws  are  blunt,  not  capable  of  being  retracted. 
The  numerous  races  of  dogs  cannot  be  sharply 
marked  off  from  each  other,  nor  can  some  of  the 
varieties  of  the  dog  be  sharply  differentiated  from 
wolves.  The  wolf  has  usually  erect  ears  and  larger 
teeth,  but  no  absolute  point  of  difference  can  be 
relied  upon.  The  fox  has  an  oval  pupil  and  a  more 
bushy  tail.  All  the  true  dogs  have  comparatively 
smooth  tongues. 

The  family  Felidcz,  or  cats,  are  also  digitigrade 
carnivores,  but  they  differ  from  the  Canidce,  or  dogs, 
in  having  the  claws  capable  of  retraction  when  not  in 
use,  and  thus  they  are  preserved  from  undue  friction 
and  are  sharp  ;  the  retraction  is  accomplished  by 
mean  3  of  lateral  elastic  ligaments.  The  cats  are 
more  purely  flesh-eaters  than  the  dogs,  and  usually 
hunt  and  kill  their  prey  ;  their  dentition  is 


3—3  I—  I  2—2  I  -I 

The  lion  is  a  native  of  Africa  and  Asia,  the  tiger,  the 


104  Vertebrata. 

strongest  of  the  carnivores,  is  confined  to  Asia, 
Other  forms  are  the  panthers  and  leopards,  the  ounce, 
the  jaguar  or  American  leopard,  the  puma  or 
American  lion,  the  tiger-cats,  ocelots,  lynx,  and 
domestic  cats.  This  last-named  is  probably  the 
descendant  of  the  wild  cat  of  Abyssinia  tamed  by  the 
ancient  Egyptians.  The  wild  cat  of  this  country 
(Lynx  canadensis),  ranges  over  the  entire  continent 
south  of  the  Arctic  circle.  The  cheetah,  or  hunting 
leopard  of  India,  has  only  partially  retractile  claws. 
The  cats  have  all  rough  tongues  armed  with  numer- 
ous sharp,  recurved  papillae. 

The  hyaenas  are  intermediate  in  some  respects 
between  the  dogs  and  the  cats.  They  have  the 
dentition  and  rough  tongues  of  the  cats,  with  a  more 
doglike  form  and  non-retractile  claws.  They  are 
nocturnal,  and  can  be  known  by  the  peculiarly  low 
hind-quarters  in  comparison  with  the  fore. 

Civets  and  mongooses  make  another  family  called 
Vtverridtz,  which  usually  possess  odorous  glands, 
rough  tongues,  short  legs,  and  a  semi-plantigrade 
mode  of  progression.  The  weasel  and  otter  family, 
Mustelida,  differ  from  these  in  their  shorter,  rounder 
heads,  smooth  tongues,  and  longer  bodies.  Many  of 
these  are  sought  for  on  account  of  their  skins,  such  as 
the  vison,  ermine,  sable,  mink,  &c.  Others,  like  the 
weasel,  skunk  and  pole-cat,  are  well-known  vermin ; 
the  Mustela  foina,  or  marten,  was  the  domestic  cat  of 
the  classic  authors. 

The  plantigrade  carnivores  are  those  that  bring 
their  whole  foot- sole  to  the  ground  when  walking; 
they  are  bears,  badgers,  and  kinkajous.  The  badgers 


Bears,  Badgers,  Kinkajoiis. 


105 


have   scent  glands,  whereby  they  are   easily  distin- 
guished.    The  kinkajou,  a  native  of  South  America, 


has  a  prehensile  tail  and  retractile  claws.    The  best 


io6  Vertebrata. 

known  of  the  bears  are  the  polar  or  white  beai  of  the 
Arctic  regions,  the  black  bear  of  America,  the  brown 
bear  of  Europe,  and  the  grizzly  bear  of  the  Rocky 
Mountains,  possibly  the  same  as  the  giant  cave  bear, 
now  extinct  in  these  countries.  The  brown  bear 
formerly  inhabited  the  British  Islands,  but  was  extir- 
pated in  Scotland  in  the  eleventh  century. 

The  bears  differ  from  the  other  carnivores  in  the 
possession  of  tubercled  teeth  which  can  be  used  for 
masticating  vegetable  matters,  and  many  of  them  are 
capable  of  partaking  of  a  mixed  diet. 

64.  Order  10,  Hyraooidea. — A  small  order  inclu- 
ding a  few  little  tail-less  animals,  natives  of  Africa  and 
Syria,    one  of  which  is  the  cony,  mentioned  in  the 
Bible.     They  are  somewhat  rabbit-like  in  habit,  with 
four  toes  on  the  fore  feet,  and  three  on  the  hinder, 
each  toe  being  armed  with  a  flat  nail.     The  molar 
teeth  have  been  compared  in  pattern  to  those  of  the 
rhinoceros,  and   there  are  no   canines.     They  have 
sacculated  stomachs  and  no  collar-bones. 

65.  Order  11,  Bodentia.— Gnawing  animals,  the 
largest  order  in  the  entire  class,  including  the  rats,  mice, 
squirrels,  &c.     They  are  all  small  and  claw-bearing, 
and   have   a   most  remarkable  dentition.     There    is 
usually  but  one  incisor  on  each  side  of  each  jaw,  and 
this  tooth  is  chisel-shaped  ;  it  consists  of  two  materials, 
one  a  hard  substance   or  enamel  on  the  outside  or 
front,  the  other  a  softer  dentine  or  bone-like  substance 
behind.     In  their  growth  the  upper  and  lower  teeth 
oppose  each  other,  and  the  constant  friction  during 
feeding  wears  away  the  surface  of  the  tooth,  which 
however  is  constantly  growing,  but  as  the  soft  dentine 


Teeth  of  Gnawing  Mammals. 


107 


wears  away  more  quickly  than  the  harder  enamel,  the 
tooth  is  kept  constantly  sharp ;  hence  when  one 
incisor  in  a  rodent  is  broken,  the  one  that  should 


FIG.  51. 


Flying  squirrel. 

oppose  it  grows  on  continuously,  and  sometimes  this 
mode  of  growth  locks  the  jaws  together. 

There  are  no  canine  teeth  in  rodents,  and  the 


io8  Vertebrata. 

molars  are  separated  from  the  incisors  by  a  long 
interspace.  The  lower  jaw  is  large,  and  its  condyle 
is  so  articulated  as  to  permit  it  to  slide  backwards 
and  forwards  in  mastication,  thus  giving  the  power  of 
gnawing. 

FIG.  52. 


Skull  of  porcupine,  showing  v,  the  large  infra-orbital  cavity. 

Rodents  have  small,  smooth  brains,  usually  a 
simple  or  saccular  stomach,  and  a  long  caecum  or 
blind  pouch  from  the  intestine  (except  in  dormice). 
Some  genera,  like  guinea-pigs,  hares,  and  rabbits,  have 
no  collar-bones,  others,  like  squirrels  and  beavers, 
have  these  bones  well  marked.  The  hares  and  rabbits 
have  a  thin  layer  of  enamel  surrounding  the  backing 
of  dentine  on  the  incisor  teeth,  and  have  two  small 
incisors  behind  the  large  ordinary  pair  in  the  upper 
jaw. 

The  squirrel  family  are  usually  long-tailed  elegant 
creatures,  and  in  one  genus,  the  flying  squirrel  (fig.  5 1 ), 
there  is  a  lateral  parachute  of  skin  stretching  from  the 
fore  to  the  hind  limbs.  The  beavers  have  flat  scaly- 
tails  and  webbed  hind  feet.  The  rats  and  mice 


Gnawing  Animals.  109 

are  known  by  their  long  cylindrical  scaly  tails,  and 
usually  rooted  teeth  (except  in  the  voles).  The 
common  grey  rat,  introduced  from  the  banks  of  the 

FIG.  53- 


ihe  spaiax,  or  blind  rat. 

Volga  in  1727  into  Western  Europe,  has  now  nearly 
exterminated  the  black  rat.  Spaiax  (fig.  53),  the  rat- 
mole  of  SE.  Europe  and  NW.  Asia,  has  rudimental 
eyes  covered  by  the  skin,  and  Dipus,  the  jerboa  of  the 
East,  has  long,  kangaroo-like  hind  legs  and  very 
small  fore  legs.  The  porcupines  have  a  covering  of 
quill-like  hairs,  and  have  an  enormous  hole  in  the  front 
of  the  skull  wall,  directly  under  the  eye  (fig.  52),  which 
is  partly  occupied  by  a  muscle  of  mastication.  The 
chinchillas,  coypu,  &c.  which  are  sought  for  their  fur, 
are  also  examples  of  this  order. 

Hybernation. — Many  rodents,  like  some  mam- 
mals of  other  orders,  bears,  bats,  &c.,  spend  their 
winter  in  a  condition  of  sleep :  this  process  is  called 
hybernation.  Previous  to  retiring  to  this  rest,  these 
animals  store  up  fat  in  different  regions  of  the  body, 


1 10 


Vcrtebrata. 


especially  in  a  large  gland  called  the  thymus,  placed 
in  the  thorax,  or  cavity  of  the  chest,  in  front  of  the 
heart.  This  fat  is  absorbed  during  the  winter,  and 
the  animal  arises  next  spring  lean  and  hungry.  The 
lemmings  extend  far  north  into  the  Arctic  regions, 
some  having  been  captured  at  the  winter  quarters  of 
the  'Alert '  in  1875,  in  N.  latitude  82°. 

66.  Order  12,  Proboscidea  (Elephants). —  No 
groups  of  mammals  appear  more  diverse  from  each 
other,  in  size  at  least,  than  do  the  rodents  and  the 
elephants,  and  yet  the  latter  are  structurally  more 

FIG.  54- 


Skull  of  young  elephant. 

22,  the  premaxillary  bone,  containing  the  root  of  the  tusk  k  ;  15,  nasal  bone  ; 
7,  tempora  region:  26,  zygomatic  arch ;  i,  lower  jaw;  c,  upper  jaw. 

closely  allied  to  the  former  than  to  any  other  order 
of  mammals.     The  elephants  are  the  giants  among 


Elephants. 


in 


living  land  animals  of  the  tropics,  and  are  covered 
with  a  thick  naked,  or  sparsely  haired  skin.  They 
have  five  hoof-covered  toes  on  each  foot,  though 
sometimes  two  toes  are  included  in  one  hoof.  The 
proboscis,  or  trunk,  is  a  muscular  and  exceedingly 
movable  double-barrelled  tube  appended  to  the  nose, 

FIG  55- 


Section  of  the  skull  of  the  elephant,  showing  the  small  size  of  the  brain- 
case,  e,  and  the  large  size  of  the  air  spaces. 

b,  marks  the  posterior  nostrils  ;    13,  the  cavity  of  the  nose  ;  a,  the  front 
opening  of  the  bony  nostrils  to  the  edge  of  which  the  trunk  is  attached. 

in  fact  an  extension  of  that  organ,  which,  by  means 
of  a  finger-like  appendage  at  the  tip,  can  pick  up  even 


112  Vertebrate 

exceedingly  small  objects.  The  teeth  of  an  elephant 
consist  of  two  tusks  or  incisors  in  the  upper  jaw, 
which  grow  continuously,  sometimes  to  enormous 
sizes,  and  furnish  the  ivory  of  commerce.  There  are 
no  incisors  in  the  lower  jaw,  but  there  are  on  each 
side  of  each  jaw  two  large,  rough-crowned,  quadrate 
teeth,  whose  crowns  are  marked  by  transverse  enamel 
ridges,  used  in  grinding  the  twigs  and  shoots  of  trees 
on  which  these  animals  feed.  There  is  a  constant 
succession  of  these  molars,  seven  of  which  are  de- 
veloped during  the  life  of  the  animal  on  each  side  of 
each  jaw,  but  never  more  than  two,  or  at  most  three, 
are  laterally  functional  at  one  time.  The  skull  is 
enormous,  most  of  its  bulk  consisting  of  huge  air- 
cells,  and  the  brain  is  large  and  convoluted  on  the 
surface.  Two  species  of  elephants  are  now  living, 
confined  to  the  tropics :  one  in  Africa,  known  by  its 
convex  forehead  and  flapping  ears  ;  one  in  India, 
which  has  a  concave  forehead  and  smaller  ears. 
Formerly  several  species  of  elephants  lived  in  Europe, 
and  remains  of  one  form  have  been  abundantly  met 
with  in  some  parts  of  the  British  Islands.  In  Siberia, 
also,  there  exist  numerous  remains  of  a  hair-clad  ele- 
phant, the  mammoth,  which  had  probably  existed 
down  to  a  comparatively  modern  time. 


H3 
CHAPTER  XVIII. 

LEMURS,  MOLES,  AND   EATS. 

67.  Order  13,  Prosimii. — The  lemurs,  which 
constitute  this  little  order,  are  monkey-like  animals, 
chiefly  confined  to  the  Island  of  Madagascar,  and  to 
other  islands  in  the  Indian  Ocean.  They  are  arbo- 
real, fruit-  or  insect-eating  animals,  with  an  opposable 
thumb  on  the  fore  foot,  and  sometimes  on  the  hind 
foot  as  well,  the  second  toe  of  which  always  bears  a 
long  claw,  while  all  the  others  usually  have  flat-nails 
like  those  on  the  human  fingers.  In  some  respects 
the  animals  resemble  the  sloths  of  the  New  World, 
and  many  of  them  are  nocturnal.  Their  teeth  are 
always  of  the  four  kinds,  and  are  more  numerous 
than  those  of  man.  They  are  clad  in  an  exceedingly 
soft  and  thick  fur,  and  many  of  them  have  bushy  tails, 
while  others,  like  the  Loris,  or  slow  lemurs,  are  per- 
fectly tailless.  The  largest  forms  measure  about  three 
feet  in  length,  but  some  are  much  smaller,  being  only 
a  few  inches  long.  Many  zoologists  regard  them,  on 
account  of  their  opposable  thumbs,  as  closely  allied 
to  the  monkeys ;  but  in  their  simple  brains  and  in 
the  structure  of  some  of  their  internal  organs,  they 
represent  a  much  lower  grade  of  organisation  than 
that  of  the  monkeys.  The  aye-aye  of  Madagascar,  a 
strange  little  animal,  about  the  size  of  a  rabbit,  has 
nails  only  on  its  thumbs,  and  claws  on  the  other 
fingers.  One  singular  genus  from  the  Philippine  and 


Vertebrata. 


FIG.  56. 


Malay  Islands,  Tarsius,  has  the  tarsus  or  ankle-bones 
of  the  foot  exceedingly  long,  like  the  corresponding 
bones  in  the  frog,  so  that  it  appears  to  have  two  ankle 
joints. 

68.  Order  14,  Insectivora. — This  order  of  -mam- 
mils  consists  of  the  shrews,  moles,  and  hedgehogs, 
which,  as  their  name  implies,  feed  on  insects  and 
worms,  and  other  small  animals.  They  are  all  of 
small  size,  and  possess  strong  claws,  long  tapering 
snouts,  and  numerous  sharply  pointed  teeth,  the 
canines  being  small  or  absent.  They  all  possess 
complete  collar  bones,  a  character  which  distinguishes 

them  from  Carnivores, 
and  gives  to  the  fore- 
limbs  a  fixity  and  defi- 
niteness  of  action  that 
would  be  otherwise 
wanting.  Their  brains 
are  usually  small  and 
smooth,  not  unlike 
those  of  rodents.  In 
habit  they  are  planti- 
grade, terrestrial,  and 
usually  active.  The 
moles  are  familiar  in- 
stances, and  present  in 
the  highest  degree  the 
character  of  a  fossorial  or  digging  animal ;  the  paddle- 
like  hand  the  square  arm-bone  or  humerus  (fig.  56, 
53),  and  the  enormous  muscularity  of  the  fore-limb 
enable  it  to  dig  with  wonderful  celerity  in  pursuit  of 
the  worms  and  insects  on  which  it  feeds,  while  the 


Bones  of  fore-limb  of  mole. 

52,  scapula  ;  53,  humerus  ;  54,  55, 
fore-arm  bones. 


Moles  and  Bats.  115 

velvety  skin,  and  the  rudimental  eyes  and  outer  ears, 
give  it  the  greatest  degree  of  fitness  for  its  subter- 
ranean life.  Moles  are  common  in  America  and 
Great  Britain,  but  are  absent  from  Ireland.  The 
shrew-mouse  and  the  hedgehog  are  equally  common 
types  ;  the  former  can  be  easily  distinguished  from 
the  true  mice  by  the  structure  of  the  teeth.  The  pigmy 
shrew  of  S.E.  Europe  is  the  smallest  known  mammal, 
being  only  about  two  inches  long.  The  flying  lemurs 
of  the  East  Indian  archipelago,  which  form  the  last 
family  of  this  order,  have  a  wide  parachute-like  mem- 
brane stretching  from  the  fore-limbs  to  the  hind,  and 
thence  to  the  tail.  They  form  a  connecting  link  be- 
tween this  order  and  the  next. 

69.  Order  15,  Cheiroptera  (Bats). — This  curious 
group  of  mammals  includes  the  only  forms  in  the 
entire  class  which  have  any  true  powers  of  flight,  the 
so-called  flying  phalangers,  flying  squirrels,  and  flying 
lemurs  having  only  the  power  of  taking  long  leaps, 
In  the  bats  the  fore  limbs  are  very  long,  the  fingers 
are  enormously  lengthened,  and  are  united  togethei 
by  an  extensive  and  thin  membrane,  which  stretches 
from  finger-tip  to  finger-tip,  and  from  thence  to  the 
hind  limb;  the  thumb  alone  is  free,  and  it  is  always 
armed  with  a  claw.  The  outline  of  this  membrane 
is  shown  by  the  dotted  line  in  fig.  57.  They  are 
mostly  nocturnal,  with  smooth  brains  and  feeble 
powers  of  sight,  and  are  rarely  of  large  size.  To 
move  the  wings  they  are  provided  with  powerful 
pectoral,  or  breast  muscles,  and  there  is  often  an  im- 
perfect keel  on  the  sternum,  for  muscular  attachment 
They  have  also  long  and  strong  clavicles.  Their  hind 

I  2 


Vertebrata. 


limbs  are  turned  outwards  in  a  peculiar  manner,  so 
that  the  knees  bend  backwards,  and  the  great  toes  are 


Bats.  117 

thus  twisted  to  the  outer  side  of  the  foot,  which  has 
five  equal  claw-bearing  toes.  Many  bats  have  enor- 
mous ears,  others,  like  the  vampires  of  South  America, 
have  sensitive  leaf-like  organs  on  their  noses,  made 
up  of  complicated  folds  of  skin  overlying  processes 
of  gristle.  The  body  is  covered  with  soft  hairs  whose 
surface  presents  a  peculiar  and  characteristic  scaly 
appearance  under  the  microscope,  and  the  fronts  of 
the  wings  are  extremely  sensitive.  They  rest  by 
hooking  on  to  branches  or  ledges  by  the  Curved  claws 
of  their  hind  toes,  and  many  of  them  thus  feed  with 
their  heads  downwards.  They  are  extremely  awkward 
in  progression  on  the  ground,  and  rarely  resort  to  this 
method  of  locomotion.  Most  of  the  bats  of  temperate 
climates  hybernate,  and  these  are  almost  all  insecti- 
vorous, having  sharp-pointed  teeth  like  those  of  the 
Insectivora.  In  warmer  regions  of  the  New  World 
there  are  numerous  large  species,  such  as  the  vam- 
pires, which  are  suctorial  in  habit,  sucking  the  blood 
of  large  animals,  for  which  purpose  they  have  sharp 
lancet-like  teeth,  and  a  long  suctorial  stomach.  In 
the  tropics  of  the  Old  World  there  are  the  largest 
individuals  of  the  order,  the  fruit  bats  or  Pteropi, 
which  inhabit  the  Asiatic  and  insular  shores  of  the 
Indian  Ocean.  They  have  blunt  teeth,  moderate  ears, 
and,  in  one  species,  the  distance  from  tip  to  tip  of 
the  wings  is  often  as  much  as  five  feet.  They  are 
sometimes  called  flying  foxes,  from  their  prevailing 
colour  and  the  shape  of  their  heads. 


Ii8  Vertebrata. 

CHAPTER  XIX. 

MONKEYS.       MAN. 

70.  Order  16,  Primates.  —  This,  the  last  and 
highest  order  of  mammals,  includes  the  most  highly 
organised  members  of  the  entire  animal  kingdom  —  • 
the  monkeys,  apes,  and  mankind.  They  all  possess 
opposable  thumbs  on  some  of  the  extremities,  and 
(except  among  the  marmosets)  flat  nails  in  place  of 
claws.  The  face  is  mostly  naked  though  fringed  with 
hairs.  The  teeth  are  of  three  kinds  and  thirty-two 
in  number,  the  formula  being  usually 


2  -  2          I  -  1          2  -  2  3  -  3 

They  have  the  highest  proportional  development  of 
brain  of  all  animals,  and  the  fore-limbs  are  chiefly  set 
apart  to  wait  on  the  head.  There  are  four  sub-orders 
included:  — 

1.  The  marmosets  of  South  America,  gregarious 
small  monkeys  of  a  squirrel-like  habit,  which  have 
sharply  tubercled   teeth,  claw-like   nails   on  all   the 
digits,  except  the  great  toe,  which  alone  bears  a  flat 
nail.     The  long  fur-clad  tail  is  incapable  of  grasping, 
and  the  thumb  is  scarcely  opposable. 

2.  The  American  monkeys,  which  differ  from  all 
others  in  having  an   additional  premolar  tooth  on 


each  side  of  each  jaw  (P  ^  —  *).     They  have  for  the 

o      3 
most   part   prehensile  tails,  and   the  thumb   of  the 


Monkeys.  119 

hand  is  not  well  developed,  or  is  absent  as  in  the 
spider  monkeys  :  on  all  their  fingers  they  have  thick 
convex  nails.  Most  of  these  live  in  the  woods  of 
Brazil,  and  are  found  in  troops.  The  howling 
monkeys  have  a  drum-like  enlargement  of  the  tongue 
bone  at  the  top  of  the  larynx  or  organ  of  voice,  and 
with  it  they  can  produce  a  loud  booming  sound, 
audible  for  nearly  a  mile.  In  all  the  American 
monkeys  the  nostrils  are  separated  by  a  very  broad 
partition,  their  ear-drums  or  tympanic  bones  in  the 
skull  have  also  wide  oval  mouths. 

3.  The  Old  World  monkeys  and  apes  are  charac- 
terised by  having  a  narrow  nasal  septum,  and  the  ear- 
drums have  a  long  tubular  mouth.  The  dentition  is 

similar  to  that  of  man,  the  premolars  being  -  -2. 

They  have  almost  always  an  opposable  thumb  on  the 
hand  as  well  as  on  the  foot,  though  it  is  rarely  as 
perfect,  and  the  muscle  which  bends  it  is  never  sepa- 
rate from  the  common  flexor  muscle  of  the  other 
fingers.  The  baboon  family  may  be  known  by  pos- 
sessing cheek  pouches,  and  callous  patches  whereon 
they  sit,  as  well  as  by  their  elongated  jaws.  The  true 
baboons  have  dog-like  muzzles  and  very  short  tails  ; 
they  are  confined  to  Africa  and  Arabia,  and  some  of 
them  have  curiously  coloured  faces;  thus  the  mandrill, 
with  its  blue,  deeply-grooved  cheeks,  its  brilliant 
scarlet  lips  and  nostrils,  and  its  white  beard,  is  a 
most  striking-looking  creature.  Some,  like  the  Bar- 
bar}7  ape,  the  only  species  which  now  lives  in  Europe, 
have  no  visible  tails  ;  others,  like  the  cercopitheci  or 
green  monkeys,  have  long  tails,  but  these  organs  are 


120 


Vertebrata. 


FIG.  58. 


Skeleton  of  siamang. 


never  prehensile. 
Many,  like  the 
macaques  of  East- 
ern Asia,  have 
long  and  promi- 
nent canine  teeth, 
but  these  are  wea- 
pons of  offence, 
not  indicative  of 
a  carnivorous  diet. 
The  sacred  mon- 
key of  India  (Sem- 
nopithecus),  and 
the  thumb-less 
Colobus  of  Africa, 
have  no  cheek- 
pouches,  but  pos- 
sess long  tails  and 
callosities,  while 
the  highest  group 
of  the  sub-order, 
the  so-called  an- 
thropoids, have 
no  tails,  callosi- 
ties, nor  cheek 
pouches.  The 
chimpanzee  is  a 
black-haired  ape, 
a  native  of  Guinea, 
which  sometimes 
reaches  a  height 
of  five  feet.  The 


Man.  121 

orang-utan,  a  larger  brown-haired  species,  with  longer 
arms  and  a  larger,  rounder  head,  is  found  in  Borneo 
and  Sumatra.  The  gorilla,  the  largest  of  the  anthro- 
poids, is  a  native  of  Senegambia,  and  is  nearly  as  tall 
as,  but  much  stouter  than,  a  man.  The  gibbons  of 
Southern  Asia  differ  from  the  anthropoids  in  having 
callosities,  and  resemble  the  orangs  in  the  enormous 
length  of  their  arms  (fig.  58). 

4.  Man  is  the  last  and  highest  type  included  in 
the  order,  and  though  in  an  anatomical  point  of  view 
there  are  not  a  sufficiently  numerous  series  of  differ- 
ences of  kind  to  lead  us  to  form  of  him  a  separate 
order,  yet  there  are  enormous  differences  of  degree, 
even  of  such  kinds  as  are  cognisable  by  the  zoologist, 
who,  from  the  difficulties  incident  thereto,  cannot 
easily  take  psychological  considerations  into  account 
in  constructing  a  classification. 

Man  has  a  rudimentary  (though  an  almost  com- 
plete) hair  clothing,  and  a  perfectly  opposable  thumb 
on  the  hand,  moved  by  independent  muscles,  while 
the  great  toe  is  only  capable  of  grasping  by  approxi- 
mation, not  by  opposition,  and  even  this  power, 
though  great  in  some  savage  tribes,  is  almost  des- 
troyed, in  civilised  races,  by  the  habit  of  wearing 
shoes.  The  arms  in  man  are  shorter,  and  the  hind 
limbs  longer  and  stronger  than  in  any  of  the  apes. 
Progression  is  bipedal,  and  the  feet  are  plantigrade, 
while  the  arms  are  specially  and  solely  set  apart  for 
waiting  upon  the  head.  The  muscles  which  keep 
the  body  erect,  such  as  those  of  the  back,  the  ex- 
tensors of  the  hip-joint,  and  the  muscles  of  the  calf 
are  enormously  greater  than  are  the  corresponding 


122 


Vertebrata. 


FIG.  59. 


parts  of  monkeys,  while  the  spinal  column  exhibits  a 
series  of  curves  so  constructed  that  the  centre  of 
gravity  falls  between  the  feet.  The  brain  of  man  is 
larger  in  relative  size  and  complexity  than  t'nat  of  any 
other  animal,  being  on  an  average  fifty  ounces  in 
weight,  while  that  of  the  orang-utan  weighs  only  about 
sixteen  ounces.  Man  is  also  capable  of  articulate 
speech,  and,  psychologically,  man  is  susceptible  of 
education,  which,  in  kind  as  well  as  in  degree,  is 
utterly  unknown  among  the  lower  animals. 

Man  also  is  capable  of  fitting  himself  for  residence 
in  any  climate,  and  having  been  thus  long  scattered 

over  the  face  of  the 
earth,  the  single 
human  species  pre- 
sents to  us  numerous 
varieties,  none  of 
which,  however,  ex- 
hibit any  approach  to 
true  specific  distinct- 
ness. These  varieties 
may  be  classed  as 
follows : 

i.  Woolly-haired 
races,  such  as  the  Negroes,  Andamanese,  and  the 
Negritos  of  the  Malay  Archipelago. 

2.  Straight-haired  races,  which  may  be, 
a.  Australioid  or  dark-skinned,  small-headed 
races,  such  as  the  aborigines  of  Australia,  the  abo- 
riginal or  hill  tribes  of  India  and  Ceylon,  possibly  the 
ancient  Egyptians,  and  the  aboriginal  races  of  the 
stone  age. 


Skull  of  negro. 


Man.  123 

b.  Turanian  races,  yellow  or  red-skinned,  mostly 
broad-headed  races,  like  the  Mongols,  Chinese,  the 
American  Indians,  &c. 

c.  Iranian  or  Indo-Germanic  races,  pale  or  olive 
races,  usually  bearded,  and  usually  with  longer  heads 
and  straighter  features. 


INDEX  AND  GLOSSARY. 


ABO 

A  BOMASUS,  the  fourth  stomach 

•*     in  ruminants,  96 
Acanthopteri,  spiny-finned  fishes,  30 
Accessory  eyes  in  Scopeline  fishes, 

29 

Acrania,  headless  vertebrates,  5 
sEpyornis,  a  gigantic  extinct  bird  ol 

Madagascar,  62 
African  mud-fishes,  14-33 
Aftershaft,  53 
Air  in  bones  of  birds,  57 
Albatross,  72 
Allantois,  a  membrane  surrounding 

the  young  of  reptiles,  birds,  and 

mammals  before  birth. 
Alligators,  52 
Alula,  the  bastard  wing,  or  feathers 

borne  on  the  thumb  in  birds,  54 
Alveoli,  the  sockets  of  the  teeth  in 

vertebrate  animals, 
A  ntblyopsis,  or  blind-fish,  29 
American  monkeys,  118 
Amphibia,  34 
—  blood  of,  36 
Amphicoelous  vertebras,  bones  of  the 

vertebral  column  which  are  hollow 

on  both  surfaces,  15 
Amphioxus  lanceolatus,  4 
A  mphiuma,  one  of  the  amphibia,  39 
Anacanthini,  soft-finned  fishes  witn 

no  swimming  bladder,  29 
Anal  fin,  14 

Anatomy  of  amphioxus,  4 
Angiiisfragilis,  43 
Animals,  vertebrate,  characters  of,  i 
Anteaters,  80-85 
Antelopes   100 
Anthropoid  apes,  120 


BAB 

Anura,  tailless  amphibians,  such  as 

frogs,  39 
Aorta,  the  large  bloodvessel  which 

conveys  the  pure  blood  from  the 

heart,  21 
Aortic  arches,  9  ;  in  reptiles,  40  ;  in 

birds,  60  ;  in  mammalia,  78 
Aplacentalia,  such  mammals  as  have 

no  placentae. 
Apteryx,    wingless   bird    of    New 

Zealand,  63 
Arch,  neural,  3 
Arch,  hyoid,  8 
Arches,  aortic,  9 

—  branchial  or  gill,  18 

—  visceral,  7 
Armadillos,  86 

—  scales  of,  74 
Arterial  cone  in  fishes,  2 
Arteries,  branchial,  21 
Articulation,   a  joint  between  two 

bones. 

Artiodactyla,  even-toed  hoofed  ani- 
mals, 93 

Asymmetry  of  flat-fishes,  31 

Atlas,  the  first  bone  of  the  vertebral 
column,  which  supports  the  head. 

Atrium  in  amphioxus,  4 

Auricle  of  heart,  9 

Australioid  races  of  man,  122 

Aves,  birds.  52 

Axolotl,  a  Mexican  amphibian,  40 

Aye  Aye,  113 


•DABOONS,  119 

•LJ     Babyroussa,  a  kind  of  pig  from 
the  Malay  Islands,  94 


126 


Index  and  Glossary. 


BAD 


Badger,  104 
Barbary  ape,  119 
Barbel,  a  river  fish,  28 
Basking  shark,  25 
Bats,  115 
Bears,  104 
Beavers,  108 
Bee-eaters,  64 

Birds,  52 
Bitterns,  71 
Blackbird,  66 
Blackcap,  67 
Blennies,  31 
Blind  amphibians,  37 

—  fishes,  29 

—  rats,  109 

—  worms,  43 

Blood  of  amphibians,  36 

—  of  fishes,  21 
--  vertebrates,  9 

—  corpuscles  of  fishes,  22 
--  of  birds,  61 

—  vessels  of  birds,  60 
--  of  fish-gills,  20 

Blowing  and  blowholes  of  whales, 

99 

Boa,  8,  46 

Body  of  vertebrate  animal,  2 
Bones,  formation  of,  17 
Bony  pike  of  California  (Lepidos- 

teus),  27 

Bony  skull,  7,  17 
Bottlenose  whales,  101 
Box  fishes,  32 

Bradypoda,  the  sloth  family,  88 
Brain  of  cod,  19 
--  craniota,  19 
--  fishes,  19 
Branchial,  pertaining  to  the  gills. 

—  arteries  of  fishes,  21 
Breathing,  10-35 
Bullfinch,  67 
Bullhead,  31 

Bunodonts,  hoofed  animals  with  tu- 

berculated  teeth,  93 
Bustard,  71 
Buzzard,  69 


pADUCOUS   gills,    gills    which 
^    fall  off  before  the  animals  reach 

maturity. 
Caecum,  the  first  part  of  the  large 

intestine. 
Caecilians, worm-like  amphibians,  37 


COB 

Calamoickthys,  African  reed  fish,  27 

Callopkis,  snake,  poison  gland  of,  48 

Camels,  96 

Canine  teeth,  the  eye-tooth,  the 
foremost  tooth  in  the  maxillary 
bone,  when  it  is  single-fanged, 
and  the  corresponding  tooth  in 
the  lower  jaw. 

Carapace,  the  upper  shield  of  a  tor- 
toise, 49 

Carnivont,  flesh-eating  mammals, 
102 

Carp,  28 

Cannate  birds,  those  with  a  keel  on 
the  breast-bone,  63 

Carotid  arteries,  neck  bloodvessels, 
78 

Carpus,  the  bones  of  the  wrist-joint. 

Cartilage  bones,  such  as  begin  their 
existence  as  masses  of  gristle,  17 

Cassowary,  62 

Catarrhine  monkeys,  old  world  mon- 
keys with  a  narrow  partition  be- 
tween the  nostrils,  119 

Cats,  103 

Cave  amphibians,  38 

Cave  b«ir,  106 

Cavities  in  the  vertebrate  body,  2 

Cebus,  South  American  monkeys. 
118 

Cephalic,  pertaining  to  the  head. 

Cephalisation,  subordination  in  func- 
tion of  limbs  to  the  head,  n 

Ceratodus,  Australian  fish,  34 

Cercopithecus,  green  monkeys,  no 

Cere,  soft  skin  at  the  base  of  the 
horny  beak  in  birds,  68 

Cerebrum,  the  greater  or  anterior 
lobes  of  the  brain,  20 

Cetacea,  whales,  99 

Chameleons,  44 

Cheetah,  hunting  leopard  of  India, 
104 

Cheiroptera,  115 

Chelonia,  tortoises  and  turtles,  49 

Chewing  the  cud,  95 

Chimpanzee,  120 

Chinchilla,  109 

Ciconiee,  storks,  74 

Circulation  in  fishes,  20 

Civets,  104 

Clavicle,  the  collar-bone. 

Claws  of  cats,  10? 

Cloaca,  the  cavity  into  which  the 
intestine  and  excretory  organs 
open,  79 

Cobra,  hooded  snake,  asp,  48 


Index  and  Glossary. 


127 


coc 

Coccygomorpha,  the  cuckoo  order 
of  birds,  64 

Coccyx,  the  rudimental  tail  in  the 
higher  mammals. 

Cockatoos,  64 

Cod,  17,  18,  29 

Collocalia,  the  swallow  which  se- 
cretes the  'edible  bird's  nest,'  65 

Colobus,  120 

Colossochelys,  a  giant  extinct  tor- 
toise, 51 

Colubrine  snakes  (non-poisonous), 
46 

Concentration  of  segments  charac- 
teristic of  vertebrates,  10 

Condyles,  knobs  of  bone  by  which 
one  bone  forms  a  joint  with  an- 
other, 38 

Contour  feathers,  the  strong  quill- 
feathers  on  the  surface  of  a  bird,  53 

Coots,  71 

Coracoid  bone,  one  of  the  bones  of 
the  fore  part  of  the  shoulder- 
girdle,  56,  79 

Coral  snake,  48 

Cormorants,  73 

Corncrake,  71 

Corpuscles,  microscopical  bodies 
found  floating  in  blood. 

—  of  blood  in  amphib.a,  36 

birds,  61 

fishes,  22 

CorvicUe,  the  crow  family,  67 

Cows,  97 

Coypu,  109 

Cranes,  71 

Craniota,  skull-bearing  vertebrates, 

Cranium,  the  skull  of  a  vertebrate 

animal,  7 
Crocodilia,  51 
Crows,  67 
Ctenoid    scales,    fish-scales  with   a 

comb-like  hinder  edge,  14 
Cuckoos,  64 
Curruca,  black-caps,  67 
Cuticle,  the  outer  layer  of  the  skin. 
Cycloid  scales,  thin  bony  fish-scales 

with  a  smooth  rounded   margin, 

13 


DAB,  flat-fish,  30 
Dasypeltis,  snake,  teeth  in  the 
gullet  of,  48 
Dasyurus,  Tasmanian  devil,  81 


EEL 

Dasypus,  armadillo,  87 
Deer,  98 

Dental  formulas,  77 
—  formula  of  cat,  103 

dog,  103 

horse,  91 

kangaroo,  84 

man,  78 

marsupials,  84 

pig>  94 

ruminants,  98 

seal,  102 

sloths,  89 

_ —  Tasmanian  devil,  77 

Dentine,    the    ivory    substance    o' 

teeth,  13,  25 
Dentition,  the  arrangement  of  teeth 

in  an  animal. 
Dennis,  or  true  skin,  of  fishes,  12 

reptiles,  40 

Diaphragm,  the  muscular  partition 

between  the  cavity  of  the  ches' 

and  that  of  the  abdomen,  60,  78 
Digestive  system  of  birds,  58 

frogs  and  tadpoles,  36 

sharks,  25 

Diphycercal    tails,     tails    in    fishes 

with  an  even  marginal  fringe  of 

fin  rays. 
Dipnoi,     fishes     whose     swimming 

bladder  acts  as  a  breathing  organ, 

Diprotodon,  giant   fossil  kangaroo, 

84 
Dipus,  the  jerboas,  or  jumping  rats, 

109 
Dodo,  the  extinct  gigantic  pigeon  of 

Madagascar,  69 
Dog,  103 
Dog-fishes,  15,  26 
Dolphin,  101 
Domestic  fowl,  70 
Dormouse,  108 
Dorsal  fin,  14 
Doves,  69 
Dragon,  43 
Ducks.  72 
Dugong,  89 


RAGLES,  68 

•*-'     Ear  passage,  nature  of,  8 

Echidna,     the     spiny     anteate     o) 

Australia,  79 

Edentata,  toothless  mammals,  85 
Edible  birds'  nests,  65 
Eels,  28 


128 


Index  and  Glossary. 


EGG 

Egg  cases  of  sharks,  25 

Egg  pouches  of  pipe  fishes,  32 

Eggs  of  birds,  65 

fishes,  22 

Elasmobranchs,  sharks  so  called  from 

their  laminar  gills,  23 
Electric    organ    of  gymnotus,    the 

electric  eel,  28 

malapterurus,  28 

mormyrus,  28 

torpedo,  26 

Elephants,  no 

Embryonic  characters  in  vertebral 

column  of  sharks,  24 
Embryos  of  flat  fishes,  30 
Emus,  62 
Enamel,  the   hardest  portion  of  a 

tooth,  formed  by  the  calcification 

of  the  outer  layer  or  epidermis  of 

the  tooth  papilla. 
Epidermis,  or  surface  layer  of  the 

skin  of  fishes,  12 
—  of  reptiles,  40 

Eqwus,  the  horse  and  ass  genus,  91 
Ermine,  104 

Erythacus,  robin  redbreast,  67 
Exoskeleton,  bony  deposits  in  the 

skin  or  surface  tissues,  14 
Extensor,  a  muscle  which  straightens 

a  joint. 

External  gills  in  sharks   and  am- 
phibians, 39 
Extinct  reptiles,  52 
Eye  of  amphioxus,  5 
Eyes  of  birds,  61 
snakes,  46 


T7ALCONS,  69 

Fallow-deer,  98 

Fauna,  the  collective  name  applied 
•  to  the  animals  of  a  country  or 

district. 
Feathers,  53 
Feeding  of  whales,  100 
Feet  of  birds,  59 
Felidce,  103 
Femur,  the  thigh-bone. 
Fieldfare,  66 

Fierasfer  (a  parasitic  fish),  30 
Filefishes,  32 
Finches,  67 
Fin  rays,   the  bony  filaments  and 

spines  which  are  included  in  the 

fins  of  fishes. 
Fins  of  fishes,  14-19 
Fish,  epidermis  of,  12 


GIL 

Fish,  gills  of,  8 

—  head  of,  17,  18 

—  lateral  line  of,  15 

—  notochord  in,  17 

—  scales  of,  12 

—  shape  of,  12 

—  tail  of,  12-15 

Fistularia,  or  tobacco-pipe  fish,  3 
Flat  fishes,  30 
Flounders,  30 
Flying  fishes,  32 

—  foxes,  117 

—  lemurs,  115 

—  squirrels,  107 
Forelimbs,  ii<j. 
Fossil  amphibians,  37 

—  edentates,  87 

—  elephants,  112 

—  fishes,  27 

—  horses,  91 

—  mammals,  78 

—  reptiles,  52 
Fowls  domestic,  70 
Fox,  103 

Freshwater  and  marine  fishes  con- 
trasted, 22 

—  seals,  101 
Frigate  birds,  73 
Frilled  lizards,  43 
Fruit  bats,  117 

Fry  of  salmon,  tail  of,  15 
Functional,   capable  of  performing 

any  duty,  or  of  being  useful  in  the 

economy. 
Furculum,     the    merrythought    of 

birds,  56 
Fur  seals,  102 

Q.ANGLIA,  masses  of  nerve  mat. 

Gannets,  73 

Ganoid  fishes,  fishes  with  burnished 

scales,  27 
Gar  pike,  32 
Gavials,  52 
Geckos,  43 
Geese,  72 

Gibbons,  long-armed  apes,  tax 
Gill  arches,  8-18 

—  cover,  19 

Gills  of  amphibians,  41 

—  —  fishes,  20- 2 1 

ganoids,  27 

lampreys,  24 

pipe-fishes,  32 

sharks,  25 


Index  and  Glossary. 


129 


GIL 

Gills  of  teleosts,  29 

Giraffes,  98 

Girdles  of  limbs,  8 

Gizzard,   the  muscular  stomach  of 

birds,  39 
Globe  fishes,  32 
Glutinous  hag,  23 
Gnawing  animals,  106 
Goat,  98 
Goatsucker,  65 
Gobies,  31 
Golden  pheasant,  70 
Goldfish,  28 
Gorilla,  121 
Grallce,  wading  birds,  such  as  cranes 

and  herons,  70 
Greek  tortoise,  51 
Grey  rat,  109 
Grizzly  bear,  106 
Grouse,  70 
Guillemots,  73 
Guinea  pig,  108 
Gulls,  72 
Gurnards,  31 
Gymnopkiona,   cxcilians,  or   blind 

amphibians,  37 
Gymnotus,  the  electric  eel,  28 
Gyrantes,   the  name   given  to  the 

pigeon  order,  69 


TJADDOCK,29 

A  A     Hag,  glutinous,  23 

Hair,  74 

Halibut,  30 

Hallux,  the  great  toe 

Hammer-headed  shark,  26 

Hares,  108 

Harrier,  69 

Hawfinch,  67 

Hawk,  67 

Hawksbill  turtle,  51 

Head,  n 

Hearing,  organ  of,  6 

Heart  of  amphioxus,  4 

birds,  59 

crocodiles,  51 

dipnoi,  33 

fishes,  21 

ganoids,  27 

mammals,  78 

manatees,  QO 

reptiles,  41 

—  —  sharks,  25 

teleosts,  27 

Heat  of  birds,  61 
Hedgehog,  114 


JAW 


Helen's  eel,  28 

Hemisphere  of  brain,  20 

Herons,  71 

Herring,  viscera  of,  28 

Heterocercal  tails,  fishes'  tails  in 
which  the  vertebral  column  is 
prolonged  into  the  upper  lobe  of 
the  tail,  15-25 

Hind  limbs,  8-18 

Hippopotamus,  94 

Hollow  horns,  98 

Holothurians,  sea  cucumbers,  in- 
habited by  fishes,  30 

Homocercal,  evenly  bilobed  fishes' 
tails,  15 

Honeycomb,  the  second  stomach  of 
ruminants,  96 

Hoopoe,  64 

Hornbills,  64 

Horned  owls,  68 

Horns  in  mammals,  98 

Horse,  91 

House  sparrow,  67 

Howling  ape,  119 

Humerus,  the  bone  of  the  arm. 

Humming  birds,  66 

Hump  of  camel,  96 

Hybernation,  winter  sleep,  109 

Hyenas,  104 

Hyoid  bone,  the  bone  which  sup- 
ports the  base  of  the  tongue. 

Hyracoidea,  the  order  to  which  the 
coney  belongs,  106 

Hyrax,  coney,  106 


TBIS,  71 

•*      Ide,  a  carp-like  fish,  28 
Iguana,  group  of  American  lizards, 

Ilium,  the  haunch  bone  or  side  of 

the  pelvis. 

Impeyan  pheasant,  70 
Incisor  teeth,  76 
Insectivora,  114 
Insessores,  perching  or  sparrow-like 

birds,  66 
Internal  gills,  39 
Intestine  of  shark,  25 
Iranian  races  of  man,  133 
Isinglass,  27 


TABIRU,  71 
J     Jackdaw,  67 
Jaguar,  103 
Jaw  arches,  7 


130 


Index  and  Glossary. 


JAW 


Jaws  of  .fishes,  18 
mammals,  76 

—  —  marsupials,  84 

—  —  sharks.  24 

iay,  67 
erboa,  109 
ohn  Dory,  30 
ugal  arch,  bony  arch  in  the  skull 
from  the  outside  of  the  upper  jaw 
to  the  base  of  the  joint  of  the 
lower  jaw  with  the  skull. 
Jugular,  pertaining  to  the  throat. 


T7-ANGAROO,  82 
1  *•     Kidney,  10 
Kingfishers,  64 
Kinkajou,  105 

Koala,  the  native  bear  of  Australia, 
84 

T  ABYRINTHODONTS,     fossil 
•*-*    amphibians  with  complex  teeth, 

Lacertilia,  lizards,  42 
Lamellirostres,  ducks   and   geese, 

T     ?2 

Lamprey,  17,  23 

Lancelet,  3 

Larks,  67 

Larynx,  the  organ  of  voice,  placed 
at  the  top  of  the  windpipe. 

Lateral  line  in  fishes,  15 

Leg  of  birds,  57 

Leiotrichous,  straight  haired,  122 

Lemmings,  no 

Lemur,  113 

Leopard,  104 

Lepadogaster,  31 

Lepidosiren,  mud  fish,  17,  31 

Lepidosteus,  the  bony  pike  of  Cali- 
fornia, 27 

Leptoptilus,  the  bird  which  yields 
the  Marabou  feathers,  72 

Liber,  the  third  stomach  of  rumi- 
nants,, 96 

Limb  girdles,  8,  75 

Limbs  of  boas,  8 

frogs,  39 

—  —  whales,  100 

Linnets,  67 

Lion,  102,  103 

Liver,  3-9 

Lithe,  29 

Lizards,  8,  42 


MER 

Llamas,  96 

Longipennes  gulls  and  terns,  72 

Lopnobranchii,    pipe-fishes   having 

tufted  gills,  32 
Lore,   the  space  between  the   eye 

and  the  angle  of  the  mouth  in 

birds  and  reptiles,  71 
Loris,  113 
Lump  fish,  31 
Lung,  31,  35,  37 
Lynx,  104 
Lyre-birds,  68 


TV/TACACUS,  macaques,  or  bonnet 

Af*     and  rhesus  monkeys,  120 

Macaws,  64 

Mackerel,  31 

Macrochires,     long-handed     birds, 

such  as  swifts  and  humming  birds, 

65 

Magpie,  67 

Malapterutus,  electric  organ  of,  28 
Malar  bone.     See  jugal  arch,  89 
Mammalia,    animals    that   suckle 

their  young,  74 
Man,  121 

—  tail  of,  75 

—  teeth  of,  78 
Manatee,  75—89 
Mandible,  the  lower  jaw,  55 
Mandrill,  119 

Manis,  the  scaly  anteater  or  pan- 
golin of  the  Eastern  tropics,  85 

Manyplies,  the  third  stomach  of  a 
ruminant,  96 

Marabou,  the  stork  which  yields 
ornamental  feathers,  73 

Marine  fishes,  32 

Marmosets  or  Oustitis,  118 

Marsipobranchii,^RKs,  with  pouched 
gills,  as  lampreys,  23 

Marsupialia,  pouched  mammals, 
kangaroos,  80 

Marsupial  bone,  81 

Maxilla,  the  bone  which  forms  the 
chief  part  of  the  upper  jaw,  76 

Megatherium,  gigantic  fossil  sloth, 
89 

Melisuga,  66 

Membrane  bones,  17 

Menopoma,  American  gill-bearing 
amphibians,  39 

Merganser,  72 

Mermaid's  purses,  25 

Mermaids  89 


Index  and  Glossary. 


MER 

Merrythought,  56 
Metamorphosis  of  tadpoles,  35 

—  shanges    in  form    taking    place 
during  the  processes  of  growth. 

Migration  of  birds,  73 
Milk,  74 

—  teeth,  77 
Mink,  104 
Minnow,  28 
Missel-thrush,  66 
Moa,  62 

Mocking-birds,  67 
Molar  teeth,  77 
Mole,  114 

Moloch,  spiny  lizard,  43 

Mongoose,  104 

Monitor,  43 

Monotremata,  an  order  of  mammals 
having  a  cloaca,  79 

Mormyrus,  electric  organ  of,  29 

Mother  Gary's  chickens,  72 

Moulting,  the  process  of  the  period- 
ical shedding  of  feathers,  54 

Mound  birds,  70 

Mouse,  108 

Mouth  of  whales,  100 

vertebrates,  3 

Mud  eels.  38 

—  fishes,  15,  33 
Mullets,  31 
Muscles  of  birds,  58 
Musk,  96 

—  deer,  96 

—  glands  of  crocodiles,  51 
Mustela  foina,  or  marten,  104 
Myrmecobius,  the  banded  ant-eater 

of  Australia,  84 


TVJARWHAL,  101 

1      Nature  of  sense  organs,  6 

Neck   9,  75 

Neural  arch.  3 

Newts,  39 

New  Zealand  parrots,  64 

Nightingale,  67 

Nitrogenised  waste,  10 

Nostrils  of  lamprey,  23 

Notochord,  the  gristly  rod  which 
exists  as  the  first  form  of  backbone 
in  the  earliest  stage  of  all  verte- 
brates, 2,  17,  28 

Numida,  head  of,  70 

Nuthatch,  68 


PEN 

QCCIPITAL     bone,     the     bone 

v-/  which  forms  die  back  of  the 
skull. 

Ocelot,  104 

(Esophagus,  the  gullet  or  food- 
passage  from  the  mouth  to  the 
stomach,  3,  59 

Old  world  monkeys,  119 

Operculum,  the  gill  cover  in  fishes, 
19,  28 

Ophidia,  snakes,  44 

Opisthoccelous,  vertebrate  bodies 
which  are  concave  behind  and 
convex  in  front. 

Opossums,  81 

Optic  lobes,  20 

Orang-utan,  121 

Omithorhynchus,  the  platypus  or 
duck-mole  of  Australia,  79 

Orycteropus,  Cape  ant-eater,  86 

Osprey,  72 

Ostrich,  58,  60,  64,  66 

Otter,  104 

Ounce,  103 

Oven-building  birds,  68 

Oviparous,  reproducing  by  the  ay- 
ing  of  eggs, 

Oyovmparous,  retaining  eggs  with- 
in the  body  until  they  are  hatched 

Owls,  68  Ox,  97 

Oyster-catchers,  71 

PANTHER,  103 
A       Pangolin,  86 

Papilla,  a  wart-like  projection  of  the 
dermis. 

—  feather,  54 
Paradise,  birds  of,  68 
Parasitic  fishes,  30 
Parasphenoid  bone,  the  long  bone  at 

the  base  of  the  skull  in  fishes,  36 
Parrots,  63 
Parrot  fishes,  32 
Partridges,  70 
Patella,  the  small  bone  or  'cap'  of 

the  knee-joint. 
Paunch,  96 
Peacocks,  70 
Pecten,  a  structure  in  the  eye  of 

bird,  61 
Pectoral  fins,  19-26 

—  muscles  of  bird,  58 
Peewit,  71 

Pelias,  the  viper,  47 
Pelicans  73 
Pelvis,  56,  8 1 
Penguins,  66,  73 


K  2 


132 


Index  and  Glossary. 


PER 

Perch,  31 

Perching  birds,  66 

Perennibranchiate  amphibians,  40 

Peroneus  muscle  in  leg  of  birds,  58 

Petrels,  72 

Phalanges,  the  b  nes  of  th    fingers 

and  toes. 
Pharyngognathi,     wrasses,      fishes 

with  united  pharyngeal  bones,  32 
Pharynx,    the    uppermost    part   of 

the  digestive  canal,  3 
Pheasants,  70 
Philomela,  nightingale,  67 
Phcenicura,  redstart,  67 
Physostomi,  fishes  with  a  swimming 

bladder,  28 
Pici,  woodpeckers,  64 
93 


Pigeon,  69 
Pike,  28 


Pinnipedia,  seals,  101 

Pipa,  South  American  toads  which 

carry  the  young  on  their  backs, 

40 

Pipe  fishes,  32 
Pipits,  67 
Pisces,  fishes,  n 
Placenta,  85 
Placoid  scales,  12 
Plaice,  30 
Plantain  eaters,  64 
Plantaris  muscle  in  the  bird's  leg, 

58 

Plantigrade,  a  term  applied  to  ani- 
mals which  in  walking  place  the 

entire  surface  of  the  sole  of  the 

foot  on  the  ground. 
Plastron,    the    under    shield  of   a 

turtle  or  tortoise,  49 
Platypus,  79 
Platyrrhine,     American     monkeys 

with  a  wide  nasal  septum,  119 
Plectognathi,  sunfishes  whose  upper 

jaw-bones  are  soldered  together,  32 
Pleuronectidtz,   flat-fishes,   such  as 

the  plaice,  &c.,  30 
Plovers,  71 
Poison-fangs,  47 
Poisonous  snakes,  47 
Polypterus,  Nile  ganoid  fish,  27 
Porcupine,  109 
Porpoises,  101 
Pouch  in  marsupials,  81 
Prehensile  tails,  75 
Premaxilla,  teeth  in,  77 
Premolar  teeth,  77 
Prey,  birds  of,  68 


ROA 

Primates,  118 

Proboscidea,  elephants,  no 

Pronghorn  antelope,  98 

Prosimii,  113 

Proteus,  38 

Protopterus,  the  African  mud-fish, 

Psittaci,  parrots,  63 

Pteropus,  fruit  bats,  117 

Pterygoid  arch,  55 

Pteryla:,  tracts  of  strong  feathers  in 

birds,  54 
Puffin,  73 
Puma,  103 

Purses,  mermaids',  25 
Pygopodes,  penguins,  73 

ython,  6, 


Pyt 


46 


QUADRATE  bone,  74 
>C     Quagga,  91 


•D  ABBIT,  108 

AX-    Rachis,   the  central  axis  of  a 

feather,  53 

Radius,  the  outer  bone  in  the  fore- 
arm, 40 

Raptores,  birds  of  prey,  68 
Rasores,  scraping  birds,  poultry,  70 
Rat,  108 
Ratidcz,  running  birds  with  no  keel 

on  the  breast-bone,  62 
Rat-mole,  109 
Rattlesnake,  47 
Raven,  67 
Rays,  26 
Razorbill,  73 
Rectrices,  the  strong  tail-feathers, 

Red  deer,  98 

Redstart,  67 

Reed-fish  of  Africa,  27 

Regulus,  wrens,  67 

Remora,  sucking-fish,  31 

Rennet,  96 

Reptiles,  40 

Respiration,  3,  22 

Restoration  of  lost  parts  in  reptiles, 

42 

Reticulum,  96 
Rhea,  62 
Rhinoceros,  92 
Rhinodon,  gigantic  shark,  a6 
Rhytina,  extinct  sea-cow,  89 
Ribs,  9 
Roach,  28 


Index  and  Glossary. 


133 


ROB 

Robin,  69 

Rodentia,  106 

Roebuck,  98 

Rollers,  64 

Rook,  67 

Ruminant  ia,  animals  which  chew 

the  cud,  94 
Ruminating,  95 


CABLE,  104 

•^    Sacrum,   the  united  vertebrae 

which  enter  into  the  pelvis,  75 
Saith,  fish,  29 
Salamander,  38 
Salicaria,  warblers,  67 
Salmon,  28 
Sawfish,  26 
Scales  of  amphibians,  39 

fishes,  12,  25,  28,  29,  32 

reptiles,  43 

Scapulars,  feathers  on  the  shoulder, 

Sclerotic  plates,  61 

Scopelidae,  accessory  eyes  of,  29 

Scraping  birds,  70 

Screw  propeller,  principle  of,  12 

Sea-cows,  89 

Sea-horses,  32 

Seals,  101 

Sebaceous  glands,  74 

Segments  of  skull,  7 

body,  10 

Segmental  ducts,  10 
Seltuhia,  sharks,  24 
Semnopitheci,  120 
Sense  organs  in  tadpoles,  36 

6,  15 

Shape  of  fishes,  12 
Sharks,  7,  13,  17,  24,  25 

—  external  gills  of,  39 
Sheep,  98 

Shrews,  115 

Sieboldia,  giant  salamander,  39 

Siren,  mud-eel,  38 

Sirenia,  sea-cows,  89 

Skate,  26 

Skeleton  of  bird,  55 

1 frog,  37 

• lepidosiren,  10 

—  —  mammals,  75 

—  —  sole,  15 
tortoise,  50 

Skin,  action  of,  in  respiration,  10 

—  of  amphibia,  34 
Skull,  6 

—  of  amphibian,  36 


TEA 

Skull  of  bird,  55 

elephant,  no 

fishes,  17,  18 

mammal^  75 

reptile,  41 

Skunk,  104 

Slits,  visceral,  3-6 

Sloth,  75,  88 

Smell,  20 

Snake-like  lizards,  43 

Snakes,  44 

Snipe,  72 

Sole,  15-29 

Song  thrush,  66 

Spalax,  the  blind  rat-mole  of  S. 
Europe,  109 

Sparrow,  67 

Species  of  fish,  number  of,  22 

Spermaceti,  101 

Sperm  whales,  101 

Spider  monkeys,  119 

Spiral  valve  in  shark's  intestine,  25 

Spoonbills,  72 

Squirrels,  108 

Stag,  98 

Starling,  67  , 

Steganopodes,  pelicans  and  cormo- 
rants, whose  fourth  toe  is  included 
in  the  web,  72 

Stickleback,  31 

Stomach  of  camel,  96 

ruminant,  95 

sheep,  95 

whales,  ico 

Storks,  71 

Strigops,  the  New  Zealand  ground 
parrot,  64 

Sturgeons,  17,  27 

Sucking  fishes,  31 

Sunbirds,  68 

Sunfish,  32 

Swans,  72 

Swifts,  65 

Swimming  bladder  in  fishes,  22,  29 

Swordfish,  33 

Syhna,  wood  warblers,  67 

Syrinx,  the  organ  of  voice  in  birds, 
61 


TADPOLE,  36-38 
A      Tails,  9,  15,  19,  78,  lox 
Tapirs,  91 
Tarsius,  114 
Tasmanian  devil,  77,  8z 
—  wolf,  Si 
Teal,  74 


134 


Index  and  Glossary. 


TEE 


Teeth,  10-14 

—  of  elephant,  in 

lamprey,  23 

mammals,  76 

rodents,  107 

—  —  snakes,  46 
Teguexins,  47 
Teleostei,  bony  fishes,  27 
Tench,  28 

Terns,  72 

Thorax,  the  cavity  of  the  chest,  8 

Thrushes,  67 

Thymus  gland,  1 10 

Tiger,  103 

Titmouse,  67 

Toads,  39 
Toes,  57,  82,  91 
Tongue,  8,  44,  45,  58,  79 

lorpedo,  27 
Tortoises,  49 
Toucans,  64 

Trabeculce,  processes  of  gristle  at 

^  the  base  of  the  embryo  skull,  7 

Trachinus,  weaver  fishes,  31 
Tree  frogs,  40 
Tropic  birds,  73 

Tropj'donow,  the  ringed  snake,  46 
Trout,  28 
Trumpet  fish,  31 
Trunk  of  elephant,  in 
Tunicated  worms,  relation  of  to  ver- 
tebrates, 2 

Turanian  races  of  mankind,  123 
Turkey,  70 
Turtles,  49 

TTLNA,    the   inner  bone  of  the 

^J     forearm,  40 
Ulotrichi,  woolly  haired   races   of 

man,  122 

Umbilicus  of  feather,  53 
Ungulates,  hoof-bearing  mammals, 

Urodela,  tailed  amphibians,  38 

•\7AMPJRES,  117 
v      Vanes  of  feathers,  53 
Veins  of  the  liver,  3 
Vena  portse,  the  vein  that  carries 
th<;  blood  from  the  intestines  to 
the  liver,  3 


ZEB 

Venomous  snakes,  47 

Ventral  fins,  19 

Ventricles  of  heart,  9 

Vertebra,  one  of  the  detached  cle- 

ments  of  the  backbone,  3 
Vertebral  column,  24,  29,  36,  41,  45 
Vertebrata,  characters  of,  i 
Vipers,  47 

Visceral  arches  and  slits,  3,  10 
Viscera,  organs  of  the  body. 
Vison,  104 
Viverridte,  104 
Voice  in  birds,  60.  61 
Voles,  108 
Vultures,  68 

WAGTAILS,  67 
Walrus,  io2 
Warbler,  67 

Waste  of  living  bodies,  10 
Water  hens,  71 
Water  snakes,  48 
Wattles,  70 
Waxwings,  68 
Weasels,  104 
Weevers,  31 
Whalebone,  100 
Whales,  99 

—  limbs  of,  loo 

—  teeth  of,  76 
Wheatears,  67 
Whinchat,  67 
Whiting,  29 
Widgeon,  72 
Wild  cat,  104 

Wild  swan,  windpipe  of,  72 
Wings  of  bats,  117 
Wolf!  103 
Wombat,  84 
Woodpecker,  64 
Woodquest,  76 
Wrasse,  32 
Wren,  69 

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University  of  California  Library 

or  to  the 

NORTHERN  REGIONAL  LIBRARY  FACILITY 
Bldg.  400,  Richmond  Field  Station 
University  of  California 
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ALL  BOOKS  MAY  BE  RECALLED  AFTER  7  DAYS 

•  2-month  loans  may  be  renewed  by  calling 
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•  1-year  loans  may  be  recharged  by  bringing 
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•  Renewals  and  recharges  may  be  made  4 
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DUE  AS  STAMPED  BELOW 


SEP  1  9  1997 


